Content:

SSS – Soil System Sciences

SSS2.1 – Soil threats in the Mediterranean region: Status, drivers and strategies for sustainable land use

EGU21-10093 | vPICO presentations | SSS2.1

Status, processes, and drivers of soil degradation in the Mediterranean region

Carla S. S. Ferreira, Samaneh Seifollahi-Aghmiuni, Georgia Destouni, Marijana Solomun, Navid Ghajarnia, António Ferreira, and Zahra Kalantari

Soil supports life on Earth and provides several goods and services of essence for human wellbeing. Over the last century, however, intensified human activities and unsustainable management practices, along with ongoing climate change, have been degrading soils’ natural capital, pushing it towards possible critical limits for its ability to provide essential ecosystem services. Soil degradation is characterized by negative changes in soil health status that may lead to partial or total loss of productivity and overall capacity to support human societies, e.g., against increasing climate risks. Such degradation leads to environmental, social and economic losses, which may in turn trigger land abandonment and desertification. In particular, the Mediterranean region has been identified as one of the most vulnerable and severely affected European regions by soil degradation, where the actual extent and context of the problem is not yet well understood. This study provides an overview of current knowledge about the status of soil degradation and its main drivers and processes in the European Mediterranean region, based on comprehensive literature review. In the Mediterranean region, 34% of the land area is subject to ‘very high sensitivity’ or ‘high sensitivity’ to desertification, and risk of desertification applies to over more than 65% of the territory of some countries, such as Spain and Cyprus (IPCC, 2019). The major degradation processes are: (i) soil erosion, due to very high erosion rates (>2 t/ha); (ii) loss of soil organic matter, due to high mineralization rates while the region is already characterized by low or very low soil organic matter (<2%); and (iii) soil and water salinisation, due to groundwater abstraction and sea water intrusion. However, additional physical, chemical and biological degradation processes, such as soil sealing and compaction, contamination, and loss of biodiversity, are also of great concern. Some of the degradation processes, such as soil erosion, have been extensively investigated and their spatial extent is relatively well described. Other processes, however, such as soil biodiversity, are poorly investigated and have limited data availability. In general, a lack of systematic inventories of soil degradation status limits the overall knowledge base and impairs understanding of the spatial and temporal dimensions of the problem. In terms of drivers, Mediterranean soil degradation has mainly been driven by increasing population, particularly in coastal areas, and its concentration in urban areas (and consequent abandonment of rural areas), as well as by land-use changes and intensification of socio-economic activities (e.g. agriculture and tourism). Additionally, climate change, with increasing extent and severity of extreme events (droughts, floods, wildfires), may also be a key degradation driver in this region. Improved information on soil degradation status (including spatio-temporal extent and severity) and enhanced knowledge of degradation drivers, processes and socio-economic, ecological, and biodiversity impacts are needed to better support regional soil management, policy, and decision making. Science and evidence based improvements of soil resource governance and management can enhance soil resilience to regional and global changes, and support the region to achieve related Sustainable Development Goals and the Land Degradation Neutrality targets.

How to cite: Ferreira, C. S. S., Seifollahi-Aghmiuni, S., Destouni, G., Solomun, M., Ghajarnia, N., Ferreira, A., and Kalantari, Z.: Status, processes, and drivers of soil degradation in the Mediterranean region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10093, https://doi.org/10.5194/egusphere-egu21-10093, 2021.

EGU21-10255 | vPICO presentations | SSS2.1 | Highlight

Global soil erosion: Storm on the horizon 

Pasquale Borrelli, David A. Robinson, Panos Panagos, Emanuele Lugato, Jae E. Yang, Christine Alewell, David Wuepper, Luca Montanarella, and Cristiano Ballabio

We use the latest projections of climate and land use change (year 2070) to assess potential global soil erosion rates by water erosion (interrill and rill processes) (Borrelli et al., 2020) using the RUSLE-based semiempirical modeling platform (GloSEM) (Borrelli et al., 2017). With some degree of uncertainty, GloSEM allows prediction of both state and change of soil erosion, identifying hotspots thanks to its high resolution (250 × 250 m) and predicting future variation based on projections of change in land use, soil conservation practices, and climate change.

Three alternative scenarios (2.6, 4.5, and 8.5) are tested using the Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) (LUH2 data) and 14 General Climate Models (GCMs) (WorldClim data), for a total of 42 modelling scenarios.

In the 2015 scenario, we estimate global soil erosion equal to 43 (+9.2/−7) Pg yr−1; with a study area covering ∼95.5% of the Earth’s land surface (in Borrelli et al. 2017 the study area was ~84.1% of the Earth’s land surface). The future scenarios suggest that socioeconomic developments impacting land use will either decrease (SSP1-RCP2.6–10%) or increase (SSP2-RCP4.5 +2%, SSP5-RCP8.5 +10%) water erosion by 2070. By contrast, climate projections, for all global dynamics scenarios, indicate a trend, moving toward a more vigorous hydrological cycle, which could increase global water erosion (+30 to +66%). Quantitatively, 56.1 (+20.6+ /- 16.4) Pg yr−1, 64.8 (+28.5/-21.4) Pg yr−1, and 71.6 (+32.5/-24.7) Pg yr−1 are predicted for the SSP1-RCP2.6, SSP2-RCP4.5, and SSP5-RCP8.5 scenarios, respectively.

The modeling framework presented in this study adopts standardized data in an adequate format to communicate with adjacent disciplines and moves us toward robust, reproducible, and open data science.

 

References

Borrelli, P., Robinson, D.A., Fleischer, L.R., Lugato, E., Ballabio, C., Alewell, C., Meusburger, K., Modugno, S., Schütt, B., Ferro, V. and Bagarello, V., 2017. An assessment of the global impact of 21st century land use change on soil erosion. Nature communications, 8(1), pp.1-13.

Borrelli, P., Robinson, D.A., Panagos, P., Lugato, E., Yang, J.E., Alewell, C., Wuepper, D., Montanarella, L. and Ballabio, C., 2020. Land use and climate change impacts on global soil erosion by water (2015-2070). Proceedings of the National Academy of Sciences, 117(36), pp.21994-22001.

How to cite: Borrelli, P., Robinson, D. A., Panagos, P., Lugato, E., Yang, J. E., Alewell, C., Wuepper, D., Montanarella, L., and Ballabio, C.: Global soil erosion: Storm on the horizon , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10255, https://doi.org/10.5194/egusphere-egu21-10255, 2021.

EGU21-1504 | vPICO presentations | SSS2.1

Estimation of soil loss with RUSLE during a period of increasing rainfall erosivity (1997-2018) in two-contrasted Mediterranean watersheds (southern Spain).

Juan F. Martinez-Murillo, José A. Sillero-Medina, and José D. Ruiz-Sinoga

During the last 25 years, an increasing rainfall erosivity occurred in South of Spain according to recent studies. This fact may rendered in an increment of the derived threatens from water erosion and, consequently, soil loss processes, one of the main geomorphic agent in that geographical area. This study deals with the application of RUSLE equation in two-contrasted Mediterranean mountainous watershed from 1997 to 2018. Both of them are characterised with very common ecogeomorphologic features from Mediterranean mountains but differs in the rainfall regime: one watershed shows an altitudinal gradient from dry-Mediterranean to subhumid Mediterranean climate, and the other one from semiarid to dry-Mediterranean climate.

From the methodological point of view, RULSE was applied but some modifications were introduced in its calculation: i) rainfall intensity calculated in 10-minutes instead of 30-minutes for Factor R; ii) vegetation cover estimated by means of NDVI for Factor C; and iii) validation using field inventory of soil surface components.

The results indicated differences between both watersheds given their different ecogeomorphologic conditions. The precision of using I10 let valuate better the soil loss estimation and its spatial and temporal variability. The validation with the soil surface components obtained better results in the rainiest watershed with more biotic ecogeomorphological conditions. This study is of great useful to detect priority areas to carry out revegetation plans to control erosion and floodings.

How to cite: Martinez-Murillo, J. F., Sillero-Medina, J. A., and Ruiz-Sinoga, J. D.: Estimation of soil loss with RUSLE during a period of increasing rainfall erosivity (1997-2018) in two-contrasted Mediterranean watersheds (southern Spain)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1504, https://doi.org/10.5194/egusphere-egu21-1504, 2021.

EGU21-8879 | vPICO presentations | SSS2.1

Projections of rainfall erosivity over Italy exploiting EURO-CORDEX ensemble

Monia Santini, Roberta Padulano, Guido Rianna, Marco Mancini, and Mirko Stojiljkovic

Erosion processes are caused by a combination of predisposing factors (slope, intrinsic soil properties), accelerating factors (removal of vegetation cover, altered soil properties due e.g. to fires, overgrazing, tillage) and triggering factors (water – from rain and rivers – and wind). While the first components are rather unchanging (or changing slowly) at the human time scale, the last two must deal with the consequences of global changes. Indeed, modifications in land use, land management and climate have strong feedbacks so that, from one side, lands are more and more overexploited, degraded and exposed to erosion and, on the other side, over these lands, the frequency, magnitude, duration and timing of triggering events could deviate from their “normal” conditions.

According to the well-known RUSLE soil loss estimation model, the triggering effect of rainfall for sheet and rill erosion is accounted for by means of the so-called rainfall erosivity or “R-factor”. R-factor consists of the annual summation of the erosive power of relevant storm events, averaged over a significant period of observation. For each storm event, computation of R-factors requires high-resolution rainfall information for the evaluation of the maximum rainfall intensity occurring over a time window of 30 min during the rainfall event. Due to the generally limited access to sub-hourly precipitation observations, a number of empirical models relating R-factor to easily accessible climate, physical and geographical covariates, such as rainfall data at coarse aggregation levels, have been developed for different areas of the world.

As concerns Italy, a novel empirical model is proposed relating rainfall erosivity to cumulative precipitation, elevation and latitude. Such model, calibrated for a significant selection of relevant rain gauges with available sub-hourly data, showed a good accordance with observations and a large amount of explained variance at the annual scale, with promising results also at the monthly level. The model was effectively extended to cover the whole Italian Country for the period 1981-2010 by means of gridded rainfall datasets retrievable in the Copernicus Climate Change Service (C3S) Climate Data Store (CDS), with limited performance loss, exploring the feasibility of Copernicus products for erosion-related assessments. Although affected by limitations, the proposed model is particularly suitable for applications involving future rainfall projections since it explicitly accounts for monthly cumulative precipitation as the only climate covariate, differently for other proposed methodologies also including rainfall-related variables with higher temporal resolution, whose future trends cannot be robustly evaluated with current climate modelling tools. In the present research an ensemble of twelve future rainfall projections included in the Euro-Cordex initiative, bias-adjusted by means of the ERA5-Land reanalysis dataset, is considered to account for the uncertainties coming from the use of multiple projections. The proposed approach provides a unique example of rainfall erosivity dataset accounting for a wide ensemble of bias-adjusted rainfall projections resulting from different General Circulation Models/Regional Climate Models coupling, for multiple Representative Concentration Pathway scenarios (RCP 2.6, RCP 4.5 and RCP 8.5) and different future horizons (near, 2021-2050, and far, 2051-2080, future).

How to cite: Santini, M., Padulano, R., Rianna, G., Mancini, M., and Stojiljkovic, M.: Projections of rainfall erosivity over Italy exploiting EURO-CORDEX ensemble, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8879, https://doi.org/10.5194/egusphere-egu21-8879, 2021.

EGU21-1671 | vPICO presentations | SSS2.1

Soil characteristics and erosion in the UNESCO Geopark Estrela, Portugal.

Gerald Raab, Wasja Dollenmeier, Dmitry Tikhomirov, Markus Egli, Gonçalo Vieira, Piotr Migoń, Fabio Scarciglia, Christopher Lüthgens, and Marcus Christl

In Europe, a high soil erosion risk is modelled for the Mediterranean area such as the Iberian Peninsula (e.g., EEA, 2009), while actual field data often lacks behind. Here we present the first 239+240Pu soil erosion results (last ~60 years) in the UNESCO Geopark Estrela, Portugal. We investigated soils in a former vastly glaciated and a non-glaciated area. We hypothesized that erosion rates in relatively young areas (max. about 16–20 kyr) will be distinctly higher than in old areas (several 100 kyr). We assumed that soil structure, organic matter and weathering degree in younger (natural) soils are still less favourable and do not yet protect efficiently enough soils from erosion. Besides soil erosion, we explored the weathering degree of the soil material using chemical weathering indices, determined the soil surface age using meteoric 10Be and looked at a broad set of physico-chemical soil characteristics of these two landscape settings.

A glimpse of our first Plutonium results indicates that the differences between these two settings are rather minor. Soil erosion rates in these natural conditions (Geopark) predominantly depend on slope. With increasing slope angle, a maximum soil erosion rate of ~1600 [t km-2 yr-1] is reached. Not surprisingly, the age estimates of the soils within the formerly glaciated area confirmed the start of formation after the beginning of ice-decay. The formerly glaciated area is depleted in C and N compared to the never glaciated area. In the never glaciated area, a higher soil weathering degree is found by multiple weathering indices and an overall lower SiO2 content. Although past glacial activities rejuvenated the soil material (expressed by a lower weathering degree) and affected the soil organic matter content, soil erosion susceptibility does not seem to be higher compared to never glaciated areas. Under natural conditions, a quasi-steady state with respect to soil erosion seems to be reached fairly before 20 kyrs.

How to cite: Raab, G., Dollenmeier, W., Tikhomirov, D., Egli, M., Vieira, G., Migoń, P., Scarciglia, F., Lüthgens, C., and Christl, M.: Soil characteristics and erosion in the UNESCO Geopark Estrela, Portugal., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1671, https://doi.org/10.5194/egusphere-egu21-1671, 2021.

EGU21-1787 | vPICO presentations | SSS2.1

Comparison of water-stable aggregates on different soil types and land-uses in a Portuguese Mediterranean catchment

Radek Klíč, Carla Sofia Santos Ferreira, António Ferreira, and Miroslav Kravka

Erosion is one of the main soil threats in the Mediterranean region, leading to degradation and desertification of several areas. Water stable aggregates (WSA) is a rate of the extent to which soil aggregates resist falling apart when wetted and hit by rain drops, indicating also the resistence of soil to compaction and soil quality status. This study aims to determine the WSA in differrent soils, characterized by distinct land-uses and soil types. This work is part of Ribeira dos Covões catchment research, in the suburbs of Coimbra, the largest city of central Portugal, where research dealing with soil and hydrological properties has been developed for long time. WSA were investigated for agricultural and forest soils, on both sandstone and limestone. Soil surface samples (0-10cm) were collected in December 2020, and analysed through wet sieving method which quantifies the amount of water-stable soil aggregates fractions.

Not surprisingly, the results showed that forest soils contain a much higher proportion of water-stable soil aggregates of larger fractions than agricultural soil, where the smaller fractions prevailed. Similar results have been also reported in previous studies and found during our previous research at Praha-Suchdol locality (Housle), in Czech Republic. The fraction distribution of WSA in sandstone and limestone was comparable for forest soils. In case of agricultural soils, distribution of WSA was slightly different. WSA are a relevant part of soil surface layer, with important impacts on other soil properties (e.g. soil moisture, hydrophobicity, infiltration), thus affecting the rainfall-runoff-erosion processes, previously investigated in the study area. Further research will be developed to better assess WSA differences between distinct forest types, given the relevance of vegetation species for example on hydrophobicity and WSA dynamics. A better understanding of WSA in different soil types will be useful to support improved soil management and mitigate land degradation.

How to cite: Klíč, R., Sofia Santos Ferreira, C., Ferreira, A., and Kravka, M.: Comparison of water-stable aggregates on different soil types and land-uses in a Portuguese Mediterranean catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1787, https://doi.org/10.5194/egusphere-egu21-1787, 2021.

EGU21-16224 | vPICO presentations | SSS2.1

Multi-fractional sediment fingerprinting in monitoring sediment sources in a peri-urban Portuguese catchment

Rory Walsh, Carla Ferreira, William Blake, Sam Higton, and Antonio Ferreira

This paper explores the potential for using multiple particle size fractions in a hierarchical geochemical sediment fingerprinting approach to the assessment of changes in sediment sources through time within a small Mediterranean peri-urban catchment. Conventional  sediment fingerprinting has focussed on the <63µm fraction of fine bed-sediment on the basis that this fraction represents suspended sediment, which in turn is considered dominant over bedload in catchment sediment budgets. In reality, however, coarser sediment than 63µm may form part of suspended sediment and/or occurs as relatively fast-moving fine bedload.  Furthermore, sediment sources vary in their particle size distribution and, as geochemical composition can vary with particle size, it is arguable that sediment fingerprinting studies should consider use of multiple size fractions.

This study explores this approach using <63µm, 63-125µm, 125-250 µm and 250-2000µm size fractions.  It focuses on the north-south flowing Ribeira dos Covões catchment (6.2 km2), on the outskirts of Coimbra in central Portugal. The climate is humid Mediterranean. Catchment geology is 56% sandstone (in the east), 41 % marly limestone (in the west) and 3 % alluvium. Current land-use is 56% woodland, 4 % agricultural and 40% urban (mainly residential, but also including a recently constructed enterprise park (5%) and major highway (1%)). Recent urbanization has largely occupied former agricultural land. 

The study adopts a multi-proxy sediment fingerprinting approach to assessment of changes in sediment sources, based on geochemical (elemental) characterization of the four different size fractions of fluvial bed-sediment and soil samples, using a Niton x-ray fluorescence (XRF) elemental analyser. Sampling of fluvial sediment was carried out at 33 sites within the stream network (including all significant tributaries, downstream sites and the catchment outlet). Samples were collected in July 2018 and November 2018 following contrasting ‘late-wet-season’ and ‘end-of-dry-season’ events. In July 2018, samples of potential sediment sources were collected including: (i) soil surface (0-2cm) samples at 64 locations, (ii) 17 samples from eroding channel margin sites, and (iii) 15 samples of road sediment. All fluvial and soil samples were sieved to obtain the four target size fractions. The elemental geochemistry of each sample fraction at all fluvial and source sites was derived using the XRF analyser.  (These results were added to similar datasets previously obtained on three occasions in 2012-15 in a period of enhanced urban constructional disturbance). Differences (and similarities) in geochemical signatures between the different size fractions at each survey date at and between each tributary and potential source site were assessed using a range of statistical techniques.  Messages arising are discussed. For each size fraction and survey date, Bayesian unmixing models were used in a hierarchical (confluence-based) fashion to assess the contributions of sub-catchments to downstream sites and the catchment outlet. Modelling results for the two 2018 events were validated by comparing them with suspended sediment records collected at five tributary locations and at the catchment outlet.  Although overall, the modelling was successful in indicating and quantifying significant changes in sediment sources through time within the catchment, uncertainties in interpretation of the multiple fractions are identified and discussed. 

How to cite: Walsh, R., Ferreira, C., Blake, W., Higton, S., and Ferreira, A.: Multi-fractional sediment fingerprinting in monitoring sediment sources in a peri-urban Portuguese catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16224, https://doi.org/10.5194/egusphere-egu21-16224, 2021.

EGU21-1309 | vPICO presentations | SSS2.1

Tillage-induced management impact on soil properties and initial soil erosion in degraded calcareous soils in Mediterranean fig orchard

Igor Bogunovic, Leon Josip Telak, Ivan Dugan, Carla S. S. Ferreira, and Paulo Pereira

High majority of soil erosion studies focus on cereal croplands, vineyards, olive, avocado, citrus, almond, persimmon, apple, and apricot orchards. To date, there is a lack of information about the possible impacts of tillage management on soil properties and hydrological response in fig orchards. Understanding this will be crucial to design efficient soil conservation practices and degradation control. Therefore, the aim of this research was to study the initial soil erosion in fig plantations and temporal evolution of initial soil erosion after the tillage intervention on undeveloped, Calcic Fluvisol in Dalmatia, Croatia. The study was conducted by collecting undisturbed soil samples, followed by rainfall simulations (58 mm h-1, during 30 min, over 0.785 m2 plots) in eight repetitions per measurement 2 days, 1 month, and 3 months after the intensive tillage. The results showed a clear difference among soil properties trough time. Seasonal effect significantly modifies soil properties and hydrological response. Soil bulk density and mean weight diameter increase (p < 0.05), while water holding capacity, water stable aggregates, soil organic content, and available phosphorus decrease (p < 0.05) by time after tillage. The highest runoff was measured 1 month (100.5 m3 ha-1), followed by 3 months (82 m3 ha-1), and 0 months (48.3 m3 ha-1) after tillage. Sediment losses were highest at 3 months (3488.9 kg ha-1), followed by 3.5 times lesser losses at 1 month (990.6 kg ha-1), and 8.2 times lower right after the tillage (426.1 kg ha-1). Temporal variations of soil erodibility in this study were under the influence of soil natural consolidation and precipitation. Fig orchards on young, undeveloped soils are highly erodible forms of land use and conservation practices need to be deploy in order to mitigate land degradation.

Keywords: soil physical properties, runoff, permanent plantation, short-term changes, undeveloped soil

Acknowledgments

This work was supported by Croatian Science Foundation through the project "Soil erosion and degradation in Croatia" (UIP-2017-05-7834) (SEDCRO).

How to cite: Bogunovic, I., Telak, L. J., Dugan, I., Ferreira, C. S. S., and Pereira, P.: Tillage-induced management impact on soil properties and initial soil erosion in degraded calcareous soils in Mediterranean fig orchard, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1309, https://doi.org/10.5194/egusphere-egu21-1309, 2021.

EGU21-15889 | vPICO presentations | SSS2.1

SQI: Development index and application for two contrasting mediterranean landscapes

Jose Antonio Sillero-Medina, Paloma Hueso-Gonzalez, and Jose Damián Ruiz-Sinoga

Soil quality indexes (SQIs) are very useful in assessing the status and edaphic health of soils. This is particularly the case in the Mediterranean area, where successive torrential rainfall episodes give rise to erosion and soil degradation processes; these are being exacerbated by the current climate crisis. The objective of this study was to analyze the soil quality in two contrasting Mediterranean watersheds in the province of Malaga (Spain): the middle and upper watersheds of the Rio Grande (sub-humid conditions) and the Benamargosa River (semi-arid conditions). Field soil sampling was carried out at representative sites, and the soils were subsequently analyzed for various edaphic properties in the laboratory. From the resulting data, the mean values ​​have been grouped and reclassified, and based on a multicriteria evaluation, a SQI for the study region was generated. The results show that there are major differences between the two watersheds, with optimal soil quality values being found in the Rio Grande watershed, but more unfavorable values occurring throughout most of the Benamargosa River watershed.

How to cite: Sillero-Medina, J. A., Hueso-Gonzalez, P., and Ruiz-Sinoga, J. D.: SQI: Development index and application for two contrasting mediterranean landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15889, https://doi.org/10.5194/egusphere-egu21-15889, 2021.

EGU21-7994 | vPICO presentations | SSS2.1 | Highlight

Effect of conservation agriculture practices on the resilience of Mediterranean soils to the predicted seasonal drought events

Laura Morales, María T Domínguez, Mª Belén Herrador, Engracia Madejón, and Elena Fernández-Boy

How climate change will affect soil functioning is a major concern, especially in Mediterranean agrosystems, where, according to climate change projections, the occurrence of extreme temperatures and drought events will be increased. The main objective of our experiment was to evaluate the effect of land management (tillage system) on soil resilience against a simulated dry-rewetting cycle. Soil samples were collected from an in-situ field experiment established in 2008 in the Guadalquivir Valley, where conservation agriculture practices have been tested. Three different land management practices under a typical Mediterranean wheat-legume rotation system were compared: 1) traditional tillage (TT), 2) minimum tillage (MT) and 3) no-tillage (NT). Following our hypothesis, conservation agriculture practices (reduced tillage and no-tillage) may allow a more mature soil microbial community by reducing soil perturbation, and this would result in higher resistance of soil functioning against drought periods. Soil enzyme activities (β-glucosidase, phosphatase, acetylglucosaminidase, aminopeptidase, and dehydrogenase activities), microbial functional diversity (Microresp method), and soil DNA concentration (as an index of microbial biomass) were analyzed in a base-line sampling. Afterwards, a dry-rewetting cycle was simulated under controlled conditions. 8 subsamples of 50g from each soil sample were hydrated to reach 70% of each soil water holding capacity (WHC) and kept in those conditions for a pre-incubation period of 15 days. After this period, half of the replicates were let dry for 12 days (drought), while the others were maintained at 70% WFC (controls). Finally, all replicates were rehydrated again to the initial water content during a 14 days rewetting period. During this cycle, soil respiration rates were periodically measured to study the evolution of soil microbial activity. Our results showed that initial respiration rates were slightly higher in MT compared to NT (p<0.1), likely due to higher organic C and N content in the MT soils. Drought extremely reduced respiration rates in the three treatments, but the results did not show a clear pattern among treatments. During the rewetting period, respiration rates were significantly higher in drought samples in comparison with the controls, while no significant differences were found for the land management treatments. Besides, land management practices did not have a significant effect on soil DNA concentration, functional diversity of the microbial community, or enzyme activities. To conclude, the absence of a clear effect of land management practices on soil resilience to drought may be due to the experimental conditions. An in-situ experiment will allow us to determine if tillage reduction enhances soil resilience to moisture stress.

How to cite: Morales, L., Domínguez, M. T., Herrador, M. B., Madejón, E., and Fernández-Boy, E.: Effect of conservation agriculture practices on the resilience of Mediterranean soils to the predicted seasonal drought events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7994, https://doi.org/10.5194/egusphere-egu21-7994, 2021.

EGU21-2158 | vPICO presentations | SSS2.1

The role of inter-row grass cover in steep viticulture: understanding soil erosion combining in-field observation and remote sensing

Eugenio Straffelini, Stefan Otto, Anton Pijl, Enrico Marchesini, Simone Gottardi, Nicola Tormen, Andrea Pitacco, Luca Tezza, and Paolo Tarolli

Steep slope viticulture is a common practice in the Mediterranean basin offering landscapes of considerable environmental and socio-economic value. However, these agricultural systems are very fragile. One of the main problems is soil erosion due to extreme rainfall, both for drop splash and water accumulation. This may cause a progressive reduction in soil fertility and the occurrence of instabilities and land degradation phenomena. To worsen this condition there is the soil compaction by mechanization and the intensification of severe weather events due to climate change (Tarolli and Straffelini, 2020).

Sustainable farming techniques may provide innovative solutions to reduce the risk of soil erosion. A virtuous approach involves the use of herbaceous coverings between the rows of vines, for many reasons. They provide active protection from the kinetic energy of water droplets; reduce the amount of water flowing on the surface positively affecting the infiltration capacity of the soil; improve ecosystem services in the vineyard.

This work aims to evaluate the effectiveness of different types of grass cover in terms of erosion and runoff generation in steep slope viticulture. The research is part of the SOiLUTION SYSTEM project (www.soilutionsystem.com) within the EU Rural Development Programme (Programma di Sviluppo Rurale per il Veneto 2014-2020); it is proposed to identify an integrated system of environmentally and economically sustainable interventions to reduce the risk of erosion and improve soil management in the terraced area of Soave (Veneto region), one of the two Italian GHIAS-FAO site. In particular, we have set up an experimental vineyard, where different managements are being tested, one for each inter-row of equal size and slope. Downstream of each of them, a water/sediment trap has been developed, obtaining continuous measurements of water volume and sediment concentration over two years. In this way, it is possible to compare the measures understanding the propensity of managements to generate runoff and soil erosion.

Specifically, many types of managements have been evaluated. (1) Continuous tillage, or a bare soil row; (2) Reference, a row where the farm's traditional grass cover is proposed; (3) Nectariferous, or a mix of herbaceous species capable of attracting insects and thus increasing biodiversity in the row; (3) Single tillage, or a row tilled once a year; (4) Native, or a row sown with native species of the place where the vineyard is located.

In combination with in-field experiments, an analysis was carried out on remote sensing data. The evolution of high-tech in topography permits low-cost tools and methodology to create high-resolution Digital Terrain Models (DTMs). For this purpose, we used a RPAS (Remotely Piloted Aircraft Systems) paired with Structure from Motion technique (RPAS-SfM). 3D reconstruction provides detailed knowledge of the terrain features, offering interesting insight to understand the processes that took place in the vineyard. The integrated implementation of in-field measures with remote sensing data opens new opportunities in runoff and soil erosion understanding, providing stakeholders with useful guidelines for sustainable management.

Tarolli, P., & Straffelini, E. (2020). Agriculture in Hilly and Mountainous Landscapes: Threats, Monitoring and Sustainable Management. Geography and Sustainability, 1 (1) (2020), pp. 70-76. https://doi.org/10.1016/j.geosus.2020.03.003

How to cite: Straffelini, E., Otto, S., Pijl, A., Marchesini, E., Gottardi, S., Tormen, N., Pitacco, A., Tezza, L., and Tarolli, P.: The role of inter-row grass cover in steep viticulture: understanding soil erosion combining in-field observation and remote sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2158, https://doi.org/10.5194/egusphere-egu21-2158, 2021.

Maintenance of ground cover vegetation in olive orchards has been shown to reduce soil and runoff losses as compared to bare soil. However, extrapolation of its impact at hillslope scale under different conditions still challenging for several reasons. One is the limited duration of available experiments, usually shorter than 3 years, which can´t capture the annual variability in precipitation typical of Mediterranean type of climate. A second reason is the small scale in which many experiments are carried out, which do not capture all the relevant erosion processes at hillslope scale. A third reason, hardly discussed, is the use of the runoff plots that limits traffic resulting in conditions that might not be fully representative of actual orchards.

 

For evaluating the effect of temporary cover crops on water erosion processes in olives at hillslope scale, runoff and soil losses have been monitored from 2008 to 2019 in La Conchuela. This is an olive farm located in Southern Spain, where average annual precipitation is 655 mm, on Typic Haploxerert (clay content > 50%). Six runoff plots (14x24 m) delimited by steel beams on concrete foundation were established in a 13.4 % slope, containing 3 rows of 4 trees. This allows normal farm operations. Since 2008-2009, two soil management systems, conventional tillage (CT) and temporary cover crops (CC), were tested. In the two CT plots ground vegetation was controlled by 2-3chisel ploughing passes during the year. CC in the other four plots consisted of sowing manually in mid Fall a grass or a mix with grasses every 1 to 3 years without disturbing the soil surface, been mowed in early Spring. The aim of this cover crop was to be grown up spontaneously from seed produced the previous year. Weeds along the tree rows are controlled by herbicides in both cases.

No significant differences were detected (p < 0.05) for the whole period, although CC showed lower runoff and soil losses values. Runoff data ranged from 157.7 ± 61.2 to 144.5 ± 46.4 mm, and soil losses varied from 24.3 ± 9.1 to 16.4 ± 7.0 t·ha-1 at the CT and CC treatments respectively. The lack of statistical differences can be explained by the large variability recorded in the measurements at the six plots, especially at the CC due to the specific weather and traffic conditions. Our experiment shows how in a crop, olives, subject to intense traffic during the harvesting season (happening in late fall or early winter, rainy season) and in an orchard on heavy soils, maintenance of a good cover crop is challenging in many years. Our results call for caution when extrapolating the benefits of cover crops in olives from the experimental plots to real world conditions. It also highlights the need for improved soil management under these conditions (e.g. controlled traffic, combination with inert mulch, …) to improve soil and water conservation in intensively cultivated olive orchards in heavy soils.

 

How to cite: Gomez, J. A. and Guzman, G.: Long-term evaluation of cover crops on soil and runoff losses under trafficked conditions in olive orchards, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-606, https://doi.org/10.5194/egusphere-egu21-606, 2021.

EGU21-6199 | vPICO presentations | SSS2.1

Introduction of legume cover crops practice in intensive grain corn crop system to mitigate soil threats in the Mediterranean region

Anne Karine Boulet, Carlos Alarcão, Carla Ferreira, Adelcia Veiga, Lara Campos, António Ferreira, and Rudi Hessel

In Portugal, grain corn is the main cereal produced, comprising 56% of total cereal yield. It is grown in intensive monoculture cropping systems that may have negative effects on soil quality, affecting long-term fertility and productivity, and therefore the sustainability of production. A promising management practice to mitigate soil degradation is to grow a cover crop during the usual fallow period. This study examined in which extend six species of legume cover crops (forage pea (pisum sativum L), yellow lupin (lupinus luteus), crimson clover (trifolium incarnatum), balansa clover (trifolium michelianum), persian clover (trifolium suaveolens), and arrowleaf clover (trifolium vesiculosum) are suitable to mitigate soil threats in grain corn systems specifically in the Mediterranean region. Specific objectives were to identify the effectiveness of the legume 6 species in improving soil fertility (i.e., soil organic matter content), mitigating nutrient leaching, nutrient recycling, and weed control. The study was performed in the lower Mondego valley in central Portugal. It covered two autumn to spring periods of cover crop cultivation, and assessed changes in soil fertility, dry biomass yield of legumes and weeds, and their associated nutrient content (total nitrogen-phosphorus-potassium).

In general, the six legume cover crops (LCC) species showed good adaptation to Mediterranean conditions, yielding large amounts of biomass (up to 8 ton/ha for clovers species). At the short term, LCC incorporation into the soil had no clear effect in soil organic matter content. The median uptake of NPK macronutrients for all species was high respectively 176-20-172 kg/ha, due to their generally high biomass production, highlighting their great potential to mitigate nutrient leaching. The capacity of the LCC to provide green manure services enabled a median reduction of 40% of N, 60% of P, and 100% of K supplied by mineral fertilizers necessary to attain a corn grain yield of 12t/ha. LCC showed a good effectiveness in weeds control, although only in the second year of the study. Three clover species (crimson, balansa, arrowleaf) performed best in terms of weed control maintaining weed production below 0.5 ton/ha, vs 3-4 ton/ha in control plots, due to early establishment and/or high biomass production in later growth stages, and avoiding the first application of herbicide in pre-emergent herbicide for grain corn cultivation.

How to cite: Boulet, A. K., Alarcão, C., Ferreira, C., Veiga, A., Campos, L., Ferreira, A., and Hessel, R.: Introduction of legume cover crops practice in intensive grain corn crop system to mitigate soil threats in the Mediterranean region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6199, https://doi.org/10.5194/egusphere-egu21-6199, 2021.

EGU21-91 | vPICO presentations | SSS2.1

Plant trait analysis to determine effective annual cover crops for Spanish orchards

Helena Ripley, Carly Stevens, and John Quinton

This paper investigates the use of plant trait analysis on cover crop species, and the impact selected species had on soil chemistry in a Spanish olive orchard. Farmers with hillside orchards in Spain frequently remove vegetation between tree rows due to concerns about water competition in the semi-arid environment. However, this increases the vulnerability of the soil to water erosion. Despite research showing that annual cover crops control soil loss, there has been little uptake of this form of management by farmers.

Ten species, native to southern Spain which had previously been used in cover crop experiments, and for which the seed was low cost, were assessed with plant trait analysis. Above and below ground traits, including specific leaf area, total biomass, root diameter and root volume, were examined to indicate the potential of the plants to reduce splash erosion, runoff and soil detachment. Four of the species were then selected and used in monocultures and mixes in an olive orchard set up in collaboration with CSIC in Cordoba. Soil moisture, rainfall, temperature and soil cover data was collected. Chemical analysis of plant and soil samples is to take place in January 2021.

Brachypodium distachyon, Calendula arvensis, Medicago sativa and Medicago truncatula had the most potential as cover crop species. In the field, the treatment with the greatest number of species (two grasses, one legume and one forb) had the highest mean soil cover at 78 ± 16%. It is hypothesised that the plots in which the greatest cover was established would show the greatest change in soil chemistry and that, where the legume was planted there will be higher nitrogen in the soil.

This presentation will outline the plant traits analysed, the outcomes of this analysis and the impact selected plants had on plant and soil chemistry in the field.

How to cite: Ripley, H., Stevens, C., and Quinton, J.: Plant trait analysis to determine effective annual cover crops for Spanish orchards, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-91, https://doi.org/10.5194/egusphere-egu21-91, 2021.

EGU21-7408 | vPICO presentations | SSS2.1 | Highlight

Plastic mulch in agriculture: the case of low density polyethylene and its interactions with pesticides and soil microbiota

Nicolas Beriot, Raul Zornoza, Paul Zomer, Onurcan Ozbolat, Eva Lloret, Raúl Ortega, Isabel Miralles, Esperanza Huerta Lwanga, and Violette Geissen

Low Density Polyethylene is the most applied plastic mulch in agriculture, for decreasing water evaporation, increasing soil temperature, or preventing weeds. Incomplete removal of polyethylene mulch causes plastic pollution in agricultural soils. In conventional agriculture the use of plastic mulch is combined with the use of pesticides. Little is known about the long term effects on soils of plastic debris accumulations in relation with pesticides residues.

We studied 18 parcels in vegetable farms, under organic or conventional management, where plastic mulch has been used for 5 to 20 years in Cartagena’s country side (SE Spain). We sampled soil at two depths: 0-10 cm and 10-30 cm. We compared the macro and micro plastic debris contents, the pesticides residue levels and the soil physiochemical properties between parcels. The ribosomal 16S and ITS DNA regions were sequenced to study shifts in bacterial and fungal communities, respectively. Soils under conventional management contained on average more than 6 different pesticides residues and soils in both managements contained on average 0.2±0.26 g/kg plastic debris. This study also showed how plastic and pesticides interact in soils and affect the microbial community. We identified the most sensitive groups which can act as bioindicators for plastic and pesticide pollution in soils.

How to cite: Beriot, N., Zornoza, R., Zomer, P., Ozbolat, O., Lloret, E., Ortega, R., Miralles, I., Huerta Lwanga, E., and Geissen, V.: Plastic mulch in agriculture: the case of low density polyethylene and its interactions with pesticides and soil microbiota, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7408, https://doi.org/10.5194/egusphere-egu21-7408, 2021.

SSS2.7 – Soil Erosion, Land Degradation and Conservation

EGU21-391 | vPICO presentations | SSS2.7

Changes in gully sizes: the role of interactions between land-use changes and other driving factors

Ikenna Osumgborogwu, John Wainwright, and Laura Turnbull-Lloyd

Changes in gully sizes are brought about by the interactions among gully-driving factors. The aim of this paper is to understand how interactions among land-use changes and other gully-drivers: relative relief, maximum slope, proximity to rivers and roads influence changes in gully length and gullied area. The study area covers 535 km2 in the Orlu region of southeast Nigeria. Gully heads were mapped using high resolution data (0.61 – 5m) acquired in November 2009 and December 2018 while supervised land-use classification was undertaken for both years. Three land-use classes were identified: non-vegetated, open vegetation and fallow. Geomorphic variables were acquired from the 30 m SRTM-DEM while gully head distances from rivers and roads were calculated using the distance tool in ArcGIS. Two sets of multiple regression analyses were undertaken, first to understand effects of land-use changes and secondly to ascertain influence of the other driving factors on changes in gully sizes. Non-vegetated surfaces increased from 58.6 km2 to 144.7 km2 between 2009 and 2018, while reduction in fallowed lands from 281.2 km2 to 57.8 km2 was observed. Of the 58.6 km2 of non-vegetated lands in 2009, 10.9 km2 were converted to open vegetation, while 0.18 km2 was transformed to fallow in 2018, 50.9 km2 of fallow-cover remained the same between 2009 and 2018 while 29 km2 were converted to non-vegetated and 201.3 km2 were used for open vegetation in 2018. These land use changes will likely increase volume of surface runoff.  Gully numbers grew from 26 to 39, mean gully length increased from 0.26 to 0.43 km which translates to a mean headward retreat of 17 m yr-1. Total length of all gullies changed from 10.22 to 16.63 km. Mean gullied area increased from 13775 to 16183 m2, indicating an areal retreat of 241 m2 yr-1, total gullied area grew from 0.36 km2 to 0.62 km2. Relative relief ranged between 6 – 46 m, lands around the rivers had the highest concentration of gullies, and there was a sharp rise in slope from 0 – 58.2% within a distance less than 500 m from the rivers. The first Multiple regression result indicated that associations between changes in gully length, non-vegetated and fallow land-use classes were significant at 0.05. Results of the second multiple regression analysis showed that only gully head distance from rivers had a significant positive effect on changes in gullied area. Bearing in mind the configuration of the land and rise in slope from rivers, increased volume of surface runoff (caused by changes in land use and higher slope rise) can attain higher erosive power as it approaches the river. This increased surface flow passing through gully channels on its way to the river, can enhance gully length and areal retreat.

Keywords: Gully erosion, land-use changes, gully-drivers, south east Nigeria

How to cite: Osumgborogwu, I., Wainwright, J., and Turnbull-Lloyd, L.: Changes in gully sizes: the role of interactions between land-use changes and other driving factors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-391, https://doi.org/10.5194/egusphere-egu21-391, 2021.

EGU21-1478 | vPICO presentations | SSS2.7

Influence of Ephemeral Gully Location Prediction on Soil Erosion Estimation

Chunmei Wang, Richard Cruse, Gelder Brian, Herzmann Daryl, Thompson Kelly, and James David

Predicting ephemeral gully (EG) location is essential for erosion modeling because it helps confine portions of the hillslope segment above locations that gully and channel soil loss processes dominate. In the Water Erosion Prediction Project (WEPP), the prediction of EG occurrence location influences the model results by shorting or expanding the flow path, which the hillslope erosion modeling relies on. This research aimed to analyze the sensitivity of EG locations prediction accuracy on WEPP model output within the framework of the Daily Erosion Project (DEP) at the regional scale. DEP is a near real-time estimator of precipitation, soil detachment, hillslope soil loss, and water runoff using WEPP as the erosion model. The above estimations are conducted on randomly selected and spatially distributed flowpaths, and the means are reported at the HUC12 watershed level. The flowpaths are identified based on Digital Elevation Model (DEM) grid cell and D8 connectivity to adjacent cells. A flow path starts at a cell such that all adjacent cells are at a lower elevation, that is, no other adjacent cell directs flow into it and ends when sufficient flow concentration and soil conditions occur that channel erosion processes dominate soil loss where usually EGs occurrence. In this research, the DEP flowpaths, down to and including ephemeral gully heads, were surveyed in 8 HUC12 watersheds distributed in 8 different Iowa MLRAs using high-resolution imagery in-field measurement. A grid order model was used as a method for EG location prediction. The sensitivity of accuracy of EG location prediction on WEPP/DEP soil detachment, hillslope soil loss, and water runoff model output was explored at hillslope, watershed, and regional spatial scale with both extreme rainfall events and yearly average erosion modeling. This research will allow a more clear understanding of EG prediction influence on erosion modeling and help improve the accuracy of erosion modeling by using WEPP / DEP.

How to cite: Wang, C., Cruse, R., Brian, G., Daryl, H., Kelly, T., and David, J.: Influence of Ephemeral Gully Location Prediction on Soil Erosion Estimation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1478, https://doi.org/10.5194/egusphere-egu21-1478, 2021.

The spreading use of remote techniques is in our daily life benefits to ease and/or speed up the acquisition and analysis of geographical data that can be meaningful for risk assessment or for taking decisions for prevention measures.

Here is presented one of the possible applications for the Unmanned Aerial Vehicle (UAV) acquisition, to evaluate the volume of eroded soils in a crop field due to washout after heavy rains. The case study is located North of Lausanne (Switzerland), in the village of Savigny. It is a crop field with a gentle slope where we can clearly see washout gullies appearing after rainfalls. A great number of small water streams disappeared for more intense agriculture which is the case here : According to topographical maps, a small stream was flowing in the past but disappeared  after 2004. It is interesting to see that after important rainfalls, gullies appear that could correspond to old small stream patterns. 

The data acquisition survey of October 30th, 2020 was done by means of a DJI Phantom 4 RTK flying at an altitude of about 20m and the Pix4d Capture planning mission application. To process the obtained 800 images, the new Pix4D Matic software was tested to get a fast dense point cloud with GSD ~1 cm accuracy, a DEM and an orthophoto. The dense point cloud was then analyzed with two compared methods to estimate the washout volumes, which are (1) inverse Sloping Local Base Level; and (2) Point cloud segmentation based on normal vectors and curvatures.

As a result, these two methods gave a first estimation of the eroded volume of around 15m3 over a surface of 9 hectares which corresponds to an erosion rate of 1,7m3/hectare. These remote and non-destructive techniques are fast and easy compared to conventional field surveys, and the data acquisition and processing could be automated. In conclusion, these techniques provide a relatively low-cost time-series datasets processing to monitor and quantify the ongoing gully erosion. 

Further investigation would be to keep recording the volume and erosion rate estimations after important rainfalls, when clear new gullies appear and to record in the meanwhile the rainfall intensity. This could help assess in a second step the relationship between the erosion rate and the rainfall intensity and control if this relation follows a power-law function. Such a study could also give some clues about the possible impact of climate changes on erosions in crop fields. 

How to cite: Charlotte, W., Tiggi, C., Marc-Henri, D., Li, F., and Michel, J.: Quantification of erosion rate in crop field gullies from point clouds with two different methods  : the case study of Savigny crop field (North of Lausanne, Switzerland) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2613, https://doi.org/10.5194/egusphere-egu21-2613, 2021.

EGU21-3399 | vPICO presentations | SSS2.7

Detection of soil pipe network by electromagnetic induction (EMI) in relation to the high resolution UAV data

Anita Bernatek-Jakiel, Marta Kondracka, and Maciej Liro

Subsurface erosion by soil piping is a widespread land degradation process that occurs in different soil types around the world. Recent studies have shown that piping erosion may lead to the significant soil loss and disturbances of ground surface. This process accelerates also gully erosion. However, it is still omitted in hydrological models of a catchment, as well as in soil and water erosion models. It seems that the main problem in soil piping studies lies on the basic issue, i.e., the detection of subsurface tunnels (soil pipes). As geophysical methods enable the exploration below the ground surface, they are promising in soil piping studies.

 

This study aims to evaluate the suitability of the electromagnetic induction (EMI) to detect subsurface network of soil pipes. The detailed study was conducted in the small catchment (Cisowiec) in the Bieszczady Mts. (the Eastern Carpathians, SE Poland), where pipes develop in Cambisols. The measurements were carried out using a conductivity meter EM38-MK2 (Geonics) in both vertical and horizontal measuring dipole orientations. The EM38-MK2 provided simultaneous measurements of apparent electrical conductivity with two transmitter receiver coil separation (0.5 m and 1 m). In order to compare subsurface data with the surface response (i.e., depressions and collapses), the high resolution DEM and orthophotos have been produced. These data have been prepared using Structure from Motion (SfM) technique based on the images taken from the low altitude by an Unmanned Aerial Vehicle (UAV; DJI Phantom-4 equipped with a 1' camera). The UAV-derived products (orthophotos and DEM) have the resolution of 0.014 x 0.014 m and point density of 9240 per 1 m2.

 

The EMI results are presented on the maps that gathered data at three depths (0.4 m, 0.75 m, 1.5 m). The results revealed the soil pipes as areas characterized by higher electrical conductivity than the surroundings. The spatial distribution of subsurface tunnels corresponds with the ground depressions and collapses detected in the field and seen on the high resolution DEM and orthophoto. The use of EMI in piping research has been evaluated.

 

The study is supported by the National Science Centre, Poland within the first author’s project SONATINA 1 (2017/24/C/ST10/00114).

How to cite: Bernatek-Jakiel, A., Kondracka, M., and Liro, M.: Detection of soil pipe network by electromagnetic induction (EMI) in relation to the high resolution UAV data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3399, https://doi.org/10.5194/egusphere-egu21-3399, 2021.

EGU21-3601 | vPICO presentations | SSS2.7

Predicting Soil erosion based on the machine learning in Loess Plateau of China 

Chenlu Huang and Qinke Yang

Soil erosion is one of the global ecological and environmental problems, which is an important factor leading to land degradation. To scientifically and effectively control soil erosion, it’s necessary to improve soil erosion evaluation methods that can obtain the actual rates of soil erosion, rather than potential erosion. For this, about 300 sampling units deployed in the Loess Plateau used as the basic data in our study, combining the seven soil erosion factors (rainfall-runoff erosivity factor, soil erodibility factor, slope length and steepness factor, biological-control factor, engineering-control factor, tillage practices factor) involved in the CSLE model and 50 soil erosion covariates related to climate, soil, topography, vegetation, human activities, etc. Using machine learning methods to establish an optimal model, and spatially predict the soil erosion rate and make a soil erosion mapof the entire study area. The prediction results show that the explanation degree of the random forest spatial prediction model is 73%. Among the selected optimal characteristic parameters, terrain and vegetation-related variables are the most important factors affecting soil erosion, from high to low, the order is LS > B > NDVI (May to September). Compared to previous studies with USLE/RUSLE/CSLE and GIS integrated mapping methods, or sampling survey based interpolation method, improvements in this paper can be concluded to : (1) the use of machine learning instead of simple multiply by soil erosion factors (linear regression), (2) higher resolution interpretation results supported by the project of “Pan-Third Pole Project”, which provide soil erosion that closed to the actual rates of soil erosion. (3) considerate additional related covariates such as population density, precipitation, soil conservation measures and so on. Further development of soil erosion prediction could provide a more accurate soil erosion evaluation method. This method can not only monitor and evaluate soil erosion in real time, and provide the possibility for the dynamic change analysis? of soil erosion in the future, but also help decision makers take effective measures in the process of mitigating soil erosion risk.

How to cite: Huang, C. and Yang, Q.: Predicting Soil erosion based on the machine learning in Loess Plateau of China , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3601, https://doi.org/10.5194/egusphere-egu21-3601, 2021.

EGU21-3676 | vPICO presentations | SSS2.7

Spatial Distribution and Key Prevention Areas of Ephemeral Gully under the 'Grain for Green Project' in Loess Plateau, China

Yuan Zhong, Chunmei Wang, Guowei Pang, Qinke Yang, Zitian Guo, Xin Liu, and Jianhua Su

Soil erosion is an important threat in the high-quality development of the Loess Plateau of China, and Ephemeral Gully (EG) erosion is an important erosion type. Answering the distribution characteristics of EG at the regional scale is an important basis for EG control. The regional distribution of EG and the areas that still at high risk of EG development after the 'Grain for Green Project' since more than 20 years ago remain poorly understood. This study aimed to solve the above problems by using visual interpretation based on sub-meter Google Earth images in 137 systematically selected small watersheds in the Loess Plateau. The EG density, length, land use of the hillslope where each EG existed, and other parameters were obtained and analyzed using the GIS method. The spatial distribution of EG density, average length, and spatial correlation in the Loess Plateau was explored. The current EG distribution and key prevention areas in the Loess Plateau were identified. The results showed that: (1) EGs were found in 46 surveyed watersheds accounting for 33.6% of the total watershed number, with an EG density average value of 3.41km/km2 and maximum value of 21.92 km/km2. The average number of EG was 60.32/km2. EG length was mainly distributed in 20 ~ 60 m, with an average length of 63.31 m; The critical slope length of EGs was mainly 40 ~ 60 m, with an average 56.20 m. (2) The watersheds with EGs were mainly located in the north-central, the west, and northwest of the Loess Plateau. EG erosion is extremely strong in loess hilly and gully region, and moderate in loess plateau gully region.(3) 38.3% of EG was distributed in cropland; 35.3% distributed in grassland; 22.8% distributed in forest land. After the 'Grain for Green Project', the EGs that were still distributed on cropland were a more important threat to soil erosion and need better prevention efforts. EGs located on cropland were still widely distributed in many areas of Loess Plateau, such as the northwest of Yan 'an City in the middle and upper reaches of Beiluo River, Suide and Luliang in the lower reaches of Wuding River, at the junction of Dingxi and Huining and in Qingyang area. This research would help in a more reasonable distribution of erosion control practices in the Loess Plateau.

How to cite: Zhong, Y., Wang, C., Pang, G., Yang, Q., Guo, Z., Liu, X., and Su, J.: Spatial Distribution and Key Prevention Areas of Ephemeral Gully under the 'Grain for Green Project' in Loess Plateau, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3676, https://doi.org/10.5194/egusphere-egu21-3676, 2021.

EGU21-3742 | vPICO presentations | SSS2.7

Effects of low-cost rehabilitation measures on gully sediment yields and vegetation in a savanna rangeland 

Jack Koci, Scott Wilkinson, Aaron Hawdon, Anne Kinsey-Henderson, Rebecca Bartley, and Nicholas Goodwin

Gully rehabilitation is often applied as part of catchment management aimed at reducing downstream sediment yields, yet the observed responses globally are variable. In the semi-arid tropics, there is limited data available to evaluate the performance of individual rehabilitation measures. This study investigated the effects of several low-cost gully rehabilitation strategies on sediment yields and vegetation establishment, in a savanna rangeland, north-east Queensland, Australia, over an eight-year period. Four gullies were monitored as untreated control gullies. Two gullies were subject to treatments aimed at: (i) reducing runoff to gully head cuts; (ii) increasing sediment trapping on gully floors; and (iii) increasing vegetation cover on gully walls and floors. Vegetation was monitored in nine gullies under long-term grazing exclosure as an additional reference to measure vegetation recovery. A runoff diversion structure reduced headcut erosion from 4.3 m2 y-1 to 1.2 m2 y-1. Total sediment yields were substantially lower in gullies treated with small porous check dams and cattle exclusion fencing, with mean total sediment yields reduced by 0.3-2.4 t ha y-1. These treatments, however, had negligible effect on gully fine sediment (silt and clay) yields. While sediment deposited behind porous check dams was found to contain much less fine silt and clay than parent material, it contained several times that measured in untreated gullies. Organic matter and fine material deposited behind porous check dams were sufficient to trap seeds and initiate vegetation re-establishment on the gully floor, including native perennial tussock grasses and woody trees and shrubs. In this water-limited landscape, long-term rehabilitation will be strongly influenced by prevailing climatic conditions, with periods of recovery following wetter periods, and regression during extended dry periods. Understanding linkages between rehabilitation measures, their hydrologic, hydraulic and vegetation effects and gully sediment yields is important to defining the conditions for their success.

How to cite: Koci, J., Wilkinson, S., Hawdon, A., Kinsey-Henderson, A., Bartley, R., and Goodwin, N.: Effects of low-cost rehabilitation measures on gully sediment yields and vegetation in a savanna rangeland , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3742, https://doi.org/10.5194/egusphere-egu21-3742, 2021.

EGU21-6378 | vPICO presentations | SSS2.7

Spatio-temporal dynamics of erosion and deposition in a partially restored valley-bottom gully

Alberto Alfonso-Torreño, Álvaro Gómez-Gutiérrez, and Susanne Schnabel

Soil erosion by water is a frequent soil degradation process in rangelands of SW Spain. The two main erosive processes in these areas are sheetwash erosion in hillslopes and gully erosion due to concentrated flow in valley bottoms. Land use changes and overgrazing play a key role in the genesis and development of gullies and gully erosion is a frequent process with negative consequences at the valley bottoms of these landscapes.

The development of new techniques allows monitoring of gully dynamics with an increase at spatial and temporal resolutions. Here we present a detailed study of a valley-bottom gully in a Mediterranean rangeland with a savannah-like vegetation cover that was partially restored in February 2017. Restoration activities included check dams (gabion weirs and fascines) and livestock exclosure by fencing. The objectives of this study were: (1) to analyze the effectiveness of the restoration measures, (2) to study erosion and deposition dynamics before and after the restoration activities, (3) to examine the role of micro-morphology on the observed topographic changes and (4) to compare the current and recent channel dynamics with previous studies conducted in the same study area through different methods and spatio-temporal scales, quantifying medium-term changes. Topographic changes were estimated using multi-temporal high-resolution DEMs produced using Structure-from-Motion (SfM) photogrammetry and aerial images acquired by a fixed-wing Unmanned Aerial Vehicle (UAV). DEMs and orthophotographs with a Ground Sampling Distance of 0.02 m were produced by means of SfM photogrammetric techniques. The average Root Mean Square Error (RMSE) estimated during the SfM processing was 0.03 m.

The performance of the restoration activities was satisfactory to control gully erosion. Check dams were effective favoring sediment deposition and reducing lateral bank erosion. Nevertheless, erosion was observed immediately downstream in 9% of the check dams. Livestock exclosure in the most degraded area promoted the stabilization of bank headcuts and revegetation. The sediments retained behind check dams reduced the longitudinal slope gradient of the channel bed and established a positive feedback mechanism for channel revegetation.

Keywords: gully erosion, restoration, topographic change, UAV+SfM, rangeland.

How to cite: Alfonso-Torreño, A., Gómez-Gutiérrez, Á., and Schnabel, S.: Spatio-temporal dynamics of erosion and deposition in a partially restored valley-bottom gully, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6378, https://doi.org/10.5194/egusphere-egu21-6378, 2021.

EGU21-12652 | vPICO presentations | SSS2.7

Finding strategies to reduce soil erosion using modelling tools: a case study in olive orchards of Cordoba (Spain) including sheet and rill erosion, ephemeral and permanent gullies

Iker Hernández-García, Eduardo Luquin, Rakel Gastesi, José Alfonso Gómez-Calero, José Javier López-Rodríguez, Javier Casalí, Antonio Hayas, Antonio López-Uceda, and Adolfo Peña

Agricultural activity can have a significant effect on the environment. Often, the lack of experimental data leaves simulation models as the only alternative for understanding and assessing such effects and they can be useful for exploring the response of agricultural systems to different scenarios, in order, for example, to minimize soil erosion or the pollution of watercourses by agrochemicals.

In this work we present a simulation exercise of the runoff and erosion in two typical olive groves of the Cordoba countryside with contrasting characteristics during the 2009-19 period. The model used is AnnAGNPS, widely tested and very well suited for use in agricultural environments. The specific objectives are: to analyze the applicability of the model confronting its results with data from other nearby areas; to determine the controlling factors of runoff and erosion, such as seasonality; to quantify the importance of the main types of erosion; to explore the response to two different management scenarios.

The study areas were two, Matasanos (189.4 ha of intensive olive groves on vertisols) and Morente (4.2 ha of traditional olive groves on degraded and poor vertisols). The first scenario (TC) consists of maintaining the soil bare by means of continuous conventional tillage. The second (CC) considers a temporary vegetation cover (around 70 %) on the lanes. All the possible types of erosion in those areas are considered: sheet and rill, ephemeral gullies (EG) and permanent gullies (PG). For the purposes of the simulations, the EGs are tilled while the PGs are not. The latter show more constant characteristics over time (although they also evolve), and are larger in size (i.e., they were assigned a greater depth).

The results show a significant decrease in average annual runoff in CC with respect to TC (38% in Matasanos and 55% in Morente), which is concentrated in the late autumn and winter months. Thus, according to our simulations, still preliminary, the implementation of covers would have achieved one of its objectives, which is to reduce the runoff generated in the watersheds.

The sediment yields in both watershed outlets also suffered a significant decrease in CC with respect to TC, going from 4.75 to 1.66 Mg/ha/year and from 16.2 to 6.9 Mg/ha/year in Matasanos and Morente respectively. The simulated erosion rates are consistent with observations made in the area and with other previous simulation exercises. Both sediment export and runoff show a marked seasonality, although erosion occurs somewhat more distributed throughout the year. The different types of erosion take on different importance in each watershed. For example, permanent gullies play a very important role in Morente (46% in TC and 44% in CC), despite they are active at very specific times, probably with extreme events, which is reasonable according to the observations made in the area. The results show that the model is apparently useful with respect to the proposed objectives, allowing the effect of different uses and management on the environment to be contrasted in the medium and long term.

How to cite: Hernández-García, I., Luquin, E., Gastesi, R., Gómez-Calero, J. A., López-Rodríguez, J. J., Casalí, J., Hayas, A., López-Uceda, A., and Peña, A.: Finding strategies to reduce soil erosion using modelling tools: a case study in olive orchards of Cordoba (Spain) including sheet and rill erosion, ephemeral and permanent gullies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12652, https://doi.org/10.5194/egusphere-egu21-12652, 2021.

EGU21-9591 | vPICO presentations | SSS2.7

Evaluation of the Compound Topographic Index (CTI) for the location of gullies in cultivated areas of Córdoba (Spain)

Eduardo Luquin, Yolanda Zuasti, Jorge Delgado, Raquel Gastesi, Javier Casalí, Mikel Goñi, Antonio Hayas, Adela P. Galvín, and Adolfo Peña

The identification of areas susceptible to gully formation is an objective that has important consequences for erosion control. It allows for the optimization of resources by focusing on prevention and control efforts on the most susceptible areas, avoiding the frequent evolution of ephemeral to permanent gullies. The issue is of great interest in Spanish olive groves, many of which are affected by serious problems of gully erosion.

Gullies are formed in the swales, which allows the use of topography-based tools to predict their location.

The Compound Topographic Index (CTI) proposed by Thorne et al. (1986) is calculated for each pixel as an estimate of the flow capacity to cause erosion, as it includes the product of the pixel draining area and its slope. Its application requires the identification of a critical value of the CTI (CTIc), above which the potential areas of gully occurrence will be located. Using historical orthophotos, the gullies observed were digitized for 2011 in the experimental areas called Morente (11 km2 of traditional olive groves on degraded and poor vertisols) and Matasanos (6 km2 of intensive olive groves also on vertisols) and nearby area, with cereal crops.

The objectives of this work are: to identify CTIc values corresponding to cultivated areas in Cordoba, mainly olive groves; to develop and evaluate an application that allows a user without great technical skills to obtain the CTI; to evaluate the capacity of this CTIc to reproduce gullies observed in nearby areas or in different time periods (2005) to establish cause-effect relationships between changes in landuse in this type of phenomenon, using the aforementioned tool.

Part of the digitized gullies, representative of olive grove areas, were used to obtain the CTIc of each gully, by modifying it until the best reproduction of the gullies observed was achieved, then their average value was taken as CTIc. To calculate the CTI, a 5m resolution DEM was used, obtained from LiDAR PNOA 2014.

In the framework of the Innolivar project, a desktop GIS application has been developed in a free software environment such as QGIS, which allows the calculation of the CTI. The APET tool (AGNPS Potential Ephemeral Gully Evaluation Tool) recently implemented has helped in the development of this application.

The CTI calculation by the application, after the determination of the CTIc threshold, serves to identify critical areas from a DEM, which is free and available in many countries. A first qualitative evaluation by visual verification indicates a very good characterization of the gullies. Subsequently, the goodness of fit of the gully position between the digitized gullies and the app-calculated gullies according to the CTIc is evaluated quantitatively by obtaining a binary confusion matrix by lengths. In the Morente area, an error of omission of 29% and of commission of 16% was obtained.

It can be concluded that the application generated that allows the application of the CTI methodology makes identification of areas susceptible to gully formation possible in an efficient and relatively simple manner, helping to achieve a more sustainable agriculture.

How to cite: Luquin, E., Zuasti, Y., Delgado, J., Gastesi, R., Casalí, J., Goñi, M., Hayas, A., Galvín, A. P., and Peña, A.: Evaluation of the Compound Topographic Index (CTI) for the location of gullies in cultivated areas of Córdoba (Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9591, https://doi.org/10.5194/egusphere-egu21-9591, 2021.

EGU21-13060 | vPICO presentations | SSS2.7

Spatial modelling of gully initiation in the Abaya-Chamo lakes catchments, southern Ethiopia

Liuelsegad Belayneh, Olivier Dewitte, Guchie Gulie, Jean Poesen, and Matthieu Kervyn

Lake Abaya and Lake Chamo are located within the rift valley that cuts across eastern Ethiopia. Severe soil erosion, predominantly gully erosion in the midlands and highlands, and flash flooding along rivers in the lowlands resulted in sediment and nutrient accumulation in the rift lakes. In this study, conducted in four river catchments on the Western border of the Abaya-Chamo rift, an inventory of gully channels is made and factors controlling the location of gullies are analysed. The inventory, which was prepared using Google Earth imagery and field surveys, consists of 7336 gullies over a study area of 1050 km², resulting in a high average gully density (1.56 km.km-²) with specifically high densities (3.74 km.km-²)  in the Northern Shafé river catchment. Of all mapped gullies, 56% show signs of active erosion (i.e. mostly bare gully walls and bed, and/or fresh sediments deposited in the lower parts of the gully). In order to reduce the effects of gully erosion, it is vital to understand the factors controlling gully initiation and locations most susceptible to develop new gullies. Instead of using gully head, which due to head cut retreat might not be representative of the characteristics of the gully initiation point, a slope-area threshold (SA) is used to identify the most probable gully initiation point along existing gullies. The spatial susceptibility of these sites to gully initiation is then modelled using the frequency ratio and logistic regression methods using a set of 15 geo-environmental variables related to topography, soil texture, geology, rivers, knickpoints and land cover, as potential controlling factors. Active and inactive gullies are modelled separately. Slope, type of lithology, location of knickpoint rejuvenating the landscape through channel incision, distance from roads and mean annual rainfall are identified as very important controlling factors of gully initiation sites. The most susceptible gully erosion areas are observed in the steep midland, where limited population is living, and bare land and rangeland is dominant. The results show that the models are reliable and have a good prediction performance of gully initiation when using an independent validation dataset. The produced gully susceptibility maps highlight locations where soil and water conservation or other sustainable planning actions are required. Such maps are also needed to estimate the long-term contribution of gullies to the sediments delivered to the Abaya-Chamo Lakes.

How to cite: Belayneh, L., Dewitte, O., Gulie, G., Poesen, J., and Kervyn, M.: Spatial modelling of gully initiation in the Abaya-Chamo lakes catchments, southern Ethiopia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13060, https://doi.org/10.5194/egusphere-egu21-13060, 2021.

Soil erosion as a major environmental challenge, plays a central role in land degradation. Accurate erosion rates assessment and information on erosion, deposition and on occurring processes are important to support soil protection and recovery strategies.

Due to the complexity, variability and discontinuity of erosional processes, model approaches to predict soil erosion are non-transferable to different temporal and spatial scales. Present process-based models are only valid for the particular observation scale which they were parameterized and validated for. In reality processes occur (e.g. spontaneous rill initiation) which are only to some extent reproducible, resulting in an incomplete process description. While model parameterization in the past was limited by the availability and resolution of data, constant development of data assessment technologies help overcome these confines. Time and cost in collecting data decreases, computing power is constantly expended and both the temporal and spatial resolution offer new possibilities on new scales.

Addressing the issue ‘data overhaul models’ we present a unique experimental setup, including flow velocity, erosion and deposition measurements at nested temporal and spatial scales, acquired using high resolution photogrammetric data (RGB and thermal) and structure from motion techniques. At the micro plot scale (3 m2), we perform rainfall simulations, monitored with up to eleven cameras. Using time lapse intervals of 10-20 seconds processes of pool formation and aggregate breakdown are observed. At the hillslope scale (60 m2), we installed a permanent setup – three rigs at three slope positions at four meter height, each equipped with five synchronized RGB cameras, a RGB video-camera and a low cost thermal camera. To capture changes in soil surface during rainfall events, time lapse images are triggered by a low-cost rain gauge. Soil surface changes at the small catchment scale (4 ha) are measured by taking UAV-images before and after rainfall events. These observations are used as parameterization, calibration and validation for modelled soil surface changes and erosion fluxes, using Erosion3D and FullSWOF.

The continuous development and improvement of soil erosion assessment techniques leads to spatially and temporally highly resolved information on different scales. Eventually the adjustment of the erosion models can enable a cross-scale description and validation of scale-dependent processes, offering new perspectives on both interconnectivity of sediment transport and the relationship between event frequency and magnitude.

How to cite: Epple, L., Kaiser, A., Schindewolf, M., and Eltner, A.: Data overhaul Models? – Temporal and spatial high resolution assessment techniques for across-scale calibration, parameterization and validation of physically-based soil erosion models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14339, https://doi.org/10.5194/egusphere-egu21-14339, 2021.

EGU21-1524 | vPICO presentations | SSS2.7

RUSLE Model based Assessment of Soil Erosion in Parbati River Basin, Central India using Google Earth Engine and GIS

Rohit Kumar, Benidhar Deshmukh, and Kiran Sathunuri

Land degradation is a global concern posing significant threat to sustainable development. One of its major aspects is soil erosion, which is recognised as one of the critical geomorphic processes controlling sediment budget and landscape evolution. Natural rate of soil erosion is exacerbated due to anthropogenic activities that may lead to soil infertility. Therefore, assessment of soil erosion at basin scale is needed to understand its spatial pattern so as to effectively plan for soil conservation. This study focuses on Parbati river basin, a major north flowing cratonic river and a tributary of river Chambal to identify erosion prone areas using RUSLE model. Soil erodibility (K), Rainfall erosivity (R), and Topographic (LS) factors were derived from National Bureau of Soil Survey and Land Use Planning, Nagpur (NBSS-LUP) soil maps, India Meteorological Department (IMD) datasets, and SRTM30m DEM, respectively in GIS environment. The crop management (C) and support practice (P) factors were calculated by assigning appropriate values to Land use /land cover (LULC) classes derived by random forest based supervised classification of Sentinel-2 level-1C satellite remote sensing data in Google Earth Engine platform. High and very high soil erosion were observed in NE and NW parts of the basin, respectively, which may be attributed to the presence of barren land, fallow areas and rugged topography. The result reveals that annual rate of soil loss for the Parbati river basin is ~319 tons/ha/yr (with the mean of 1.2 tons/ha/yr). Lowest rate of soil loss (i.e. ~36 tons/ha/yr with mean of 0.22 tons/ha/yr) has been observed in the open forest class whereas highest rate of soil loss (i.e. ~316 tons/ha/yr with mean of 32.08 tons/ha/yr) have been observed in gullied area class. The study indicates that gullied areas are contributing most to the high soil erosion rate in the basin. Further, the rate of soil loss in the gullied areas is much higher than the permissible value of 4.5–11 tons/ha/yr recognized for India. The study helps in understanding spatial pattern of soil loss in the study area and is therefore useful in identifying and prioritising erosion prone areas so as to plan for their conservation.

How to cite: Kumar, R., Deshmukh, B., and Sathunuri, K.: RUSLE Model based Assessment of Soil Erosion in Parbati River Basin, Central India using Google Earth Engine and GIS, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1524, https://doi.org/10.5194/egusphere-egu21-1524, 2021.

EGU21-1976 | vPICO presentations | SSS2.7

Effects of Content of Soil Rock Fragments on Calculating of Soil Erodibility

Miaomiao Yang, Qinke Yang, Keli Zhang, Yuru Li, Chunmei Wang, and Guowei Pang

【Objective】Rock fragments (>2mm diameter) are an important component of soil, and its presence has a significant impact on soil erosion and sediment yield. So it is essential to take into full account content of the rock fragments for accurate calculation of soil erodibility factor (K). 【Method】In this paper, based on the data available of the content of rock fragments and classes of soil texture with a resolution of 30 arc-second, influence of the content of rock fragments, including rock fragments in the soil profile (RFP) and gravels on the surface of the soil (SC), on K was assessed at a global scale, using the equation (Brakensiek, 1986) of the relationship between saturated hydraulic conductivity and grade of soil permeability, and the equation (Poesen) of soil erodibility attenuation under a rock fragment cover. 【Result】Results show: (1) The existence of rock fragments in the soil increased K by 4.43% and soil permeability by 5.68% on average in grade and lowering soil saturated hydraulic conductivity by 11.57% by reducing water infiltration rate of the soil and increasing surface runoff. The gravels on the surface of the mountain land and desert/gobi reduced K by 18.7% by protecting the soil from splashing of rain drops and scrubbing of runoff; so once the content of rock fragments in the soil profile and gravels on the surface of the land are taken into account in calculation, soil K may be 5.52% lower; (2)In the areas dominated with the effect of rock fragments, about 62.7% of the global land area, soil K decreased by 0.0091( t•hm2•h)•( hm-2•MJ-1•mm-1) on average, while in the area affected mainly by rock fragments in profile, about 31.1% of the global land area, soil K increased by 0.0019( t•hm2•h)•( hm-2•MJ-1•mm-1); and (3)The joint effect of rock fragments in profile and gravels on the surface reduced the soil erosion rate by 11.8% in the 6 sample areas. 【Conclusion】 The presence of RFP increases soil K while the presence of SC does reversely. The joint effect of the two leads to decrease in soil erosion. In plotting regional soil erosion maps, it is essential to take both of the two into account so as to improve accuracy of the mapping.

How to cite: Yang, M., Yang, Q., Zhang, K., Li, Y., Wang, C., and Pang, G.: Effects of Content of Soil Rock Fragments on Calculating of Soil Erodibility, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1976, https://doi.org/10.5194/egusphere-egu21-1976, 2021.

EGU21-2272 | vPICO presentations | SSS2.7 | Highlight

A grand comparison of soil & water conservation in 50 vineyards under 5 different terracing systems

Anton Pijl, Eugenio Straffelini, Wendi Wang, and Paolo Tarolli

Steep-slope agricultural landscapes often show a mosaic of diverse terraced and non-terraced hillslope configurations. The use and specific design of Soil and Water Conservation (SWC) measures such as earth bank or dry-stone wall terraces is often the result of agro-landscape evolution, and is shaped by various factors such as culture-historical values (e.g. traditional cultivation methods), agronomic development (e.g. mechanisation), site-specific conditions (e.g. local rainfall regime and construction materials), as well as environmental concerns (e.g. runoff and erosion control). Concerning the latter, the effectiveness of SWC measures is becoming increasingly urgent in the face of climate change expressed as extreme rainfall interspersed with drought periods, as commonly found in Mediterranean Europe.

While past research has provided unique insights in the impact of several terracing practices on runoff and erosion control (doi.org/10.1016/j.catena.2020.104604), this mostly focussed on descriptive analysis of detailed soil degradation patterns in a limited number of study areas. In this study, we expand this research by a comprehensive and massive evaluation of 50 vineyards cultivated by 5 different terracing and non-terracing techniques in the cultural landscape of Soave, northern Italy. This provides a grand comparison of SWC impacts based on a systematic workflow of high-resolution topographic analysis, physical erosion modelling, and statistical evaluation. Analysis is performed on a preselected set of 50 representative vineyards (10 sites for each practice) with homogeneous soil type and properties, geometric shape and size, slope positioning and steepness (calculated from 1-m LiDAR data). A set of SWC indicators is determined (e.g. average rates of soil erosion, deposition, and runoff), and are computed for each vineyard using spatially-distributed physical simulations by the Simulated Water Erosion (SIMWE) model. Simulated processes are quantified by zonal statistics, while differentiating between potential detachment and deposition hotspots (i.e. pre-determined uphill and downhill zones inside each vineyard). This allows a first indication of SWC impacts by the different hillslope configurations. Furthermore, we provide a comparison of the actual cultivated study sites and an assumed “natural scenario” (i.e. smoothed terrain, natural vegetation), in order to quantify the impacts of the 5 different terrace configurations on SWC.

Our findings provide relevant insights in the SWC effectiveness of terraced and non-terraced cultivation practices commonly found in the steep-slope agricultural landscapes of Italy. The unique experimental scale of our systematic comparison offers reliable and novel findings, which support sustainable landscape planning and management, e.g. as in our case by rural development plan Soilution System “Innovative solutions for soil erosion risk mitigation and better management of vineyards in hilly and mountain landscapes” (www.soilutionsystem.com). Future research along the same lines are encouraged in order to improve the general understanding of SWC in steep cultivation systems across diverse geographical settings.

How to cite: Pijl, A., Straffelini, E., Wang, W., and Tarolli, P.: A grand comparison of soil & water conservation in 50 vineyards under 5 different terracing systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2272, https://doi.org/10.5194/egusphere-egu21-2272, 2021.

EGU21-2464 | vPICO presentations | SSS2.7

A process-based soil erosion model ensemble to reduce model uncertainty in climate change impact assessments

Joris Eekhout, Agustín Millares-Valenzuela, Alberto Martínez-Salvador, Rafael García-Lorenzo, Pedro Pérez-Cutillas, Carmelo Conesa-García, and Joris de Vente

The impact of climate change on future soil loss is commonly assessed with soil erosion models, which are potentially an important source of uncertainty. Here we propose a soil erosion model ensemble, with the aim to reduce the model uncertainty in climate change impact assessments. The model ensemble consisted of five continuous process-based soil erosion models that run at a daily time step, i.e. DHSVM, HSPF, INCA, MMF and SHETRAN. All models simulate detachment by raindrop impact (interrill erosion), detachment by runoff (rill erosion) and immediate deposition of sediment within the cell of its origin. The models were implemented in the SPHY hydrological model. The soil erosion model ensemble was applied in a semi-arid catchment in the southeast of Spain. We applied three future climate scenarios based on global mean temperature rise (+1.5, +2 and +3 ºC). Data from two contrasting regional climate models were used to assess how an increase and a decrease in extreme precipitation affect model uncertainty. Soil loss is projected to increase and decrease under climate change, mostly reflecting the change in extreme precipitation. Model uncertainty is found to increase with increasing slope, extreme precipitation and runoff, which reveals some inherent differences in model assumptions among the five models. Moreover, the model uncertainty increases in all climate change scenarios, independent on the projected change in annual precipitation and extreme precipitation. This supports the importance to consider model uncertainty through model ensembles of climate, hydrology, and soil erosion in climate change impact assessments.

This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities - State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.

How to cite: Eekhout, J., Millares-Valenzuela, A., Martínez-Salvador, A., García-Lorenzo, R., Pérez-Cutillas, P., Conesa-García, C., and de Vente, J.: A process-based soil erosion model ensemble to reduce model uncertainty in climate change impact assessments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2464, https://doi.org/10.5194/egusphere-egu21-2464, 2021.

EGU21-2538 | vPICO presentations | SSS2.7

Straw mulch impact on soil properties and initial soil erosion processes in the maize field

Ivan Dugan, Leon Josip Telak, Iva Hrelja, Ivica Kisić, and Igor Bogunović

Straw mulch impact on soil properties and initial soil erosion processes in the maize field

Ivan Dugan*, Leon Josip Telak, Iva Hrelja, Ivica Kisic, Igor Bogunovic

University of Zagreb, Faculty of Agriculture, Department of General Agronomy, Zagreb, Croatia

(*correspondence to Ivan Dugan: idugan@agr.hr)

Soil erosion by water is the most important cause of land degradation. Previous studies reveal high soil loss in conventionally managed croplands, with recorded soil losses high as 30 t ha-1 under wide row cover crop like maize (Kisic et al., 2017; Bogunovic et al., 2018). Therefore, it is necessary to test environmentally-friendly soil conservation practices to mitigate soil erosion. This research aims to define the impacts of mulch and bare soil on soil water erosion in the maize (Zea mays L.) field in Blagorodovac, Croatia (45°33’N; 17°01’E; 132 m a.s.l.). For this research, two treatments on conventionally tilled silty clay loam Stagnosols were established, one was straw mulch (2 t ha-1), while other was bare soil. For purpose of research, ten rainfall simulations and ten sampling points were conducted per each treatment. Simulations were carried out with a rainfall simulator, simulating a rainfall at an intensity of 58 mm h-1, for 30 min, over 0.785 m2 plots, to determine runoff and sediment loss. Soil core samples and undisturbed samples were taken in the close vicinity of each plot. The results showed that straw mulch mitigated water runoff (by 192%), sediment loss (by 288%), and sediment concentration (by 560%) in addition to bare treatment. The bare treatment showed a 55% lower infiltration rate. Ponding time was higher (p < 0.05) on mulched plots (102 sec), compared to bare (35 sec), despite the fact that bulk density, water-stable aggregates, water holding capacity, and mean weight diameter did not show any difference (p > 0.05) between treatments. The study results indicate that straw mulch mitigates soil water erosion, because it immediately reduces runoff, and enhances infiltration. On the other side, soil water erosion on bare soil under simulated rainstorms could be high as 5.07 t ha-1, when extrapolated, reached as high as 5.07 t ha-1 in this study. The conventional tillage, without residue cover, was proven as unsustainable agro-technical practice in the study area.

Key words: straw mulch, rainfall simulation, soil water erosion

Acknowledgment

This work was supported by Croatian Science Foundation through the project "Soil erosion and degradation in Croatia" (UIP-2017-05-7834) (SEDCRO).

Literature

Bogunovic, I., Pereira, P., Kisic, I., Sajko, K., Sraka, M. (2018). Tillage management impacts on soil compaction, erosion and crop yield in Stagnosols (Croatia). Catena, 160, 376-384.

Kisic, I., Bogunovic, I., Birkás, M., Jurisic, A., Spalevic, V. (2017). The role of tillage and crops on a soil loss of an arable Stagnic Luvisol. Archives of Agronomy and Soil Science, 63(3), 403-413.

How to cite: Dugan, I., Telak, L. J., Hrelja, I., Kisić, I., and Bogunović, I.: Straw mulch impact on soil properties and initial soil erosion processes in the maize field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2538, https://doi.org/10.5194/egusphere-egu21-2538, 2021.

EGU21-2666 | vPICO presentations | SSS2.7

Can we use the Curve Number approach to predict gully head occurrence at the continental scale of Africa?

Sofie De Geeter, Matthias Vanmaercke, Gert Verstraeten, and Jean Poesen

Gully erosion is an important land degradation process, threatening soil and water resources worldwide. However, in contrast to sheet and rill erosion, our ability to simulate and predict gully erosion remains limited, especially at the continental scale. Nevertheless, such models are essential for the development of suitable land management strategies, but also to better quantify the role of gully erosion in continental sediment budgets. We aim to bridge this gap by developing a first spatially explicit and process-oriented model that simulates average gully erosion rates at the continental scale of Africa.

We are developing a model that predicts the likelihood of gully head occurrence by means of the Curve Number (CN) method. This model will allow to simulate the spatial patterns of gully density at high resolution (30m) based on the physical principles that control the gully erosion process by using GIS and spatial data sources that are available at the continental scale. To calibrate and validate this model, we make use of an extensive database of 44 000 gully heads mapped over 1680 sites that are randomly distributed across Africa. The exact location of all gully heads was manually mapped by trained experts, using high resolution optical imagery available in Google Earth. This allows to extract very detailed information at the level of the gully head, such as the local slope and the area draining to the gully.

Based on an explorative analysis on a subset of this dataset we found that the CN method does not directly allow to make reliable predictions on gully head occurrence within a pixel. Although land use and land cover seem to play an important role (with gully heads being clearly located in erosion-prone land use classes), the hydrological soil groups (HSGs) based on soil texture do not provide a clear relation between soils with high runoff risk and gully occurrence. A potential cause for this is likely that compensating soil effects occur: i.e. HSGs that produce low runoff volumes may be characterized by a lower soil cohesion, making them nonetheless prone to gullying. This may then cause the combination of HSG and land use to be an insignificant predictor of gully occurrence. Also uncertainties on the input data likely play an important role in this.

Overall, our results indicate that modelling gully densities using a process-oriented and spatially explicit method offers opportunities to better quantify this important land degradation process at the global scale. Nevertheless, a key challenge lies in accurately quantifying the importance of soil characteristics and especially in better understanding their relative contribution to runoff production and soil cohesion.

How to cite: De Geeter, S., Vanmaercke, M., Verstraeten, G., and Poesen, J.: Can we use the Curve Number approach to predict gully head occurrence at the continental scale of Africa?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2666, https://doi.org/10.5194/egusphere-egu21-2666, 2021.

EGU21-2707 | vPICO presentations | SSS2.7

Comparing the hydrological response of regulated vs. not regulated mountain torrents in the Mediterranean semi-arid environment: a case study in Southern Italy

Giuseppe Bombino, Daniela D'Agostino, Pietro Denisi, Antonino Labate, Pedro Perez Cutillas, Alberto Martinez Salvador, Demetrio Antonio Zema, Santo Marcello Zimbone, and Carmelo Conesa Garcia

In the Mediterranean semi-arid environment (e.g., in Southern Italy and Spain), headwaters are characterized by local factors, such as steep slopes, low drainage areas and heavy and short-duration rainstorms, which make the torrents prone to flash floods, soil erosion and landslides. The construction of check dams has contributed to mitigate the runoff and erosion rates, but the effectiveness of these structures has been rarely assessed. In these contexts, the availability of studies monitoring the mitigation effect of check dams on the hydrological response of torrents at the watershed scale over a long time could help developing new management strategies. To this aim, this study proposes an assessment of the multi-decadal runoff and erosion rates in two headwaters of torrents in Southern Italy, using a modeling approach. The first torrent (Vacale, 12.5 sq. km) is regulated by check dams built in ‘1950-1960, while the second torrent (Serra, 13.7 sq. km) is not regulated. Both catchments experienced an increase in forest cover up to the 70%, while the agricultural land decreased by about 30% of the total area after the construction of the control works until now. The hydrological response of the two headwaters has been simulated using the widely applied Hydrologic Modeling System (HEC-HMS) model for runoff and peak flow, coupled with the Modified Universal Soil Loss Equation (MUSLE) to model sediment yield. To this purpose, 10 heavy rainfall-runoff events occurred between 1956 and 1971 were modeled. The peak flows and sediment yields of the regulated watershed were compared with the corresponding simulations at the undisturbed torrent. To summarize the results of this modeling experience, the changes in land cover resulted in a noticeable decrease in flood peak discharge (on average -53%) in both torrents, while the torrent with check dams showed a significant reduction of eroded sediment for each event (on average -9%) compared to the unregulated headwater. These findings help supporting a better understanding on the impact of control works and land use changes on the hydrological responses of Mediterranean torrents, indicating the most effective strategy to mitigate flash flood hazards and heavy erosion risks in similar environmental contexts.

Acknowledgement: This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities-State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.

How to cite: Bombino, G., D'Agostino, D., Denisi, P., Labate, A., Perez Cutillas, P., Martinez Salvador, A., Zema, D. A., Zimbone, S. M., and Conesa Garcia, C.: Comparing the hydrological response of regulated vs. not regulated mountain torrents in the Mediterranean semi-arid environment: a case study in Southern Italy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2707, https://doi.org/10.5194/egusphere-egu21-2707, 2021.

EGU21-3149 | vPICO presentations | SSS2.7

Wildfire and shallows landslides: a first statistical description in Liguria (North-West Italy)

Martino Terrone, Francesco Faccini, Guido Paliaga, and Monica Solimano

Rainfall-induced shallow landslides characterize most of the geomorphological phenomena occurred in Liguria (North West Italy) in the last decades: high frequency is observed between the beginning of October and the end of April, reasonably correlated with the seasonal rainfall regime.Over the years, in national and international scientific papers, the thickness of the debris cover, the poor geotechnical characteristics of the soil, the sparse forest and shrub areas, the runoff water erosion along the slope surface were identified as landslide causal factors.However, an aspect that does not seem to be considered in Liguria Region is the causal relationship between wildfires and surface landslides.The wildfire determines a series of physical and chemical changes on the slope surface, first of all the wood and shrub cover reduction. The rapid change in land use determines an increase in the run-off and a consequent soil erosion evolving into landslides.This research aims to create a first basic statistics at regional scale among landslides and wildfire, crossing different databases and inventories, estimating a trend line both in the spatial and in the temporal domain.

How to cite: Terrone, M., Faccini, F., Paliaga, G., and Solimano, M.: Wildfire and shallows landslides: a first statistical description in Liguria (North-West Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3149, https://doi.org/10.5194/egusphere-egu21-3149, 2021.

EGU21-3698 | vPICO presentations | SSS2.7 | Highlight

Regional Scale Distribution of Gully in Loess Plateau Based on High Resolution Google Earth Satellite Imagery

Jianhua Su, Chunmei Wang, Guowei Pang, Qinke Yang, Xin Liu, Zitian Guo, and Yuan Zhong

Gully erosion is one of the most important erosion gully types in the Loess Plateau. Its generation and development seriously affect and destroy the ecological environment. Therefore, it is the premise of scientific management to make clear the spatial distribution of gully region scale. At present, scholars at home and abroad mainly focus on the spatial distribution of gully in a specific small watershed, and there are few reports on the regional scale. In view of this, this study, based on Google Earth sub meter image combined with GIS method, uses the means of manual visual interpretation to conduct sampling survey of gully in the Loess Plateau. A total of 137 sampling units were set up, and the area of each sampling unit was about 0.2 square kilometers. The results showed that: (1) there were 75 gullies in 54.7% of the survey units, with a total of 712 gullies. The sampling units with gullies were mainly located in the northeast of the Loess Plateau (yan'an-dongsheng area on both sides of the Shanxi Shaanxi Yellow River) and the middle of the Loess Plateau (the border area of Guyuan, Ningxia and Huining, Dingxi, Gansu), with an average gulley density of 3.32km/km2 and a maximum of 19.94km/km2; (2) the grassland was the most gullied area The main land use types of gully development accounted for 40.03%, followed by cultivated land and forest land, accounting for 30.06% and 20.08% respectively, and 9.83% of gully development was in bare land, orchard and residential land, collectively referred to as other land; (3) the average values of gully width, length and distance from watershed were 7.76m, 69.81m and 79.19m, respectively, and the gully width was mainly distributed in 3-5M, accounting for 50% 39.6%。 The length of gully was mainly distributed in 30-70m, accounting for 46.3%. The distance between  and watershed was mainly 25-50m, accounting for 41.6%; (4)  existed most in sub region I of Loess Plateau (22.7%), followed by sub region III of Loess Plateau (20.0%), sub region V of Loess Plateau (12.0%) and sub region II of Loess Plateau (9.3%); (5) according to the existing erosion classification standards,  erosion intensity of Loess Plateau reached strong level No. The gully density and gully length show obvious spatial differentiation characteristics. The highest density area is in yan'an-dongsheng area on both sides of Shanxi Shaanxi Yellow River, and the gully length in this area is about 100m. This study will help to better understand the spatial distribution characteristics of  in the Loess Plateau, support  management in the Loess Plateau, and promote scientific decision-making of  control in the Loess Plateau.

How to cite: Su, J., Wang, C., Pang, G., Yang, Q., Liu, X., Guo, Z., and Zhong, Y.: Regional Scale Distribution of Gully in Loess Plateau Based on High Resolution Google Earth Satellite Imagery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3698, https://doi.org/10.5194/egusphere-egu21-3698, 2021.

EGU21-4036 | vPICO presentations | SSS2.7

Spatio-temporal analysis of soil erosion in Tokoro river watershed in eastern Hokkaido, Japan

Kunihito Mihara, Kanta Kuramochi, and Ryusuke Hatano

Introduction

Accelerated erosion by human activities leads to degradation of soil ecosystem services and aquatic environment. It is unavoidable issue in Japan because it holds many sloped agricultural lands. Tokoro river watershed, TRW, in eastern Hokkaido, Japan has unique climate characterized with the least precipitation in Japan and cold winter with little snow which induces soil freezing. Frozen subsoil forms impermeable layers to increase surface runoff in early spring. The objectives of this study were i) to understand the spatial and seasonal variation of water and sediment movement in TRW using Soil and Water Assessment Tool, SWAT which is a process-based hydrological model and ii) to evaluate the impact of agricultural activities, topography of agricultural lands, and runoff characteristics on soil erosion through identification of highly erosive areas and seasons based on the simulation output.

Materials and methods

Water and sediment movement in TRW was simulated from 2011/1/1 to 2015/12/31. SWAT calculates water and sediment movement processes using spatial and temporal information of topography, land use, soil, weather, and land management in watershed. TRW was delineated into 17 subbasins based on topographic information and further divided into 764 HRUs which had homogenous combination of slope class, soil type, and land use in each subbasin. On-land processes were calculated in each HRU. After water and sediment yield from HRUs were summed in each subbasin, stream routing processes were calculated. Model parameters were calibrated so that the estimated stream flow and sediment load at the outlet would fit the measurements. From the simulation by the calibrated model, outputs were extracted as follows: 1) Contribution to the gross sediment yield and erosion rate of each land use; 2) Erosion rate of each subbasin; 3) Erosion rate of whole watershed on each month; and 4) Surface runoff and percentage of surface runoff in water yield in each month.

Results and Discussions

Calibrated SWAT reproduced well the fluctuation of stream flow and sediment load at the outlet of TRW. Although the model underestimated sediment load during large flood events with the average estimation error of -16.1±5.4% on peak-discharge months, it showed satisfactory performance with coefficient of determination: R2=0.88, Nash-Sutcliffe efficiency coefficient: Ens=0.86, and percentage of bias: PBIAS=0.34% for monthly sediment load estimation. Agricultural lands which covered 17.6% of the watershed were considered as the primary sediment sources contributing to 68.5% of estimated gross sediment yield of the watershed. Spatial variation of estimated erosion rate showed high sediment yield in the middle- and down-stream area of TRW where agricultural activities were intensive, and higher sediment yield particularly in the area where more agricultural lands had steep slopes (more than 51 t km-2 yr-1). Monthly erosion rate estimation indicated that the most severe erosion occurred on March and April (6.9±1.4 and 7.3±1.9 t km-2 mon-1 respectively). On March, average percentage of surface runoff was estimated as 90.5±6.5%. Therefore, surface runoff in early snowmelt season when the frozen subsoil prevented infiltration was considered as an important driver of soil erosion.

How to cite: Mihara, K., Kuramochi, K., and Hatano, R.: Spatio-temporal analysis of soil erosion in Tokoro river watershed in eastern Hokkaido, Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4036, https://doi.org/10.5194/egusphere-egu21-4036, 2021.

EGU21-5008 | vPICO presentations | SSS2.7 | Highlight

The impact of climate change on soil erosion: a systematic review

Joris de Vente and Joris Eekhout

Climate change is expected to cause an increase of extreme precipitation and consequently an increase of soil erosion in many regions worldwide, although large differences are reported. Therefore, this study systematically reviews research presenting projected changes in soil erosion under climate change, focussing on studies that forced soil erosion models with precipitation from climate model output. A total of 766 documents were analysed and further evaluated based on predetermined inclusion criteria, resulting in a selection of 168 documents published between 1995 and 2021. From these documents a total of 35 variables were recorded, including information related to bibliography, objective, study site, climate model, soil erosion model, land use change scenarios, soil and water conservation techniques, and the projected change in soil erosion under climate change. Studies were performed on all continents, with the majority in Europe (32%), Asia (29%) and North America (23%). The study sites were mainly located in humid continental (28%) and humid subtropical climates (22%). The studies were equally distributed over the future periods (i.e. near-, mid- and end-century) and emissions scenarios (i.e. low, intermediate and high). The majority of the studies were forced by a single climate model (44%), while 67% of the studies used a climate model ensemble smaller than 5. MUSLE (31%), RUSLE (18%) and WEPP (9%) are the most applied soil erosion models. Of these models, most were applied with a daily time step (65%). In addition to climate, the impacts of land use change and soil and water conservation techniques were considered in 13% and 17% of the studies, respectively.

Climate model output is an important source of uncertainty, therefore, we used the climate model ensemble size as a measure for uncertainty, assigning studies based on a larger climate model ensemble a larger weight in the estimation of the (weighted) median change in soil erosion under climate change. Soil erosion is projected to increase from near-century (+5% with respect to the reference period) to mid- and end-century (+17% and +15%, respectively). Soil erosion is projected to increase most in semi-arid (+23%) and humid continental climates (+20%), while soil erosion is projected to decrease in Mediterranean climates (-2%). Higher increase of soil erosion is projected for models that apply sub-daily (+26%) and daily time steps (+14%), than monthly (0%) and yearly time steps (+8%). Significantly different results were obtained between studies using bias-correction methods based on delta change (+9%) and quantile mapping (+37%). On the other hand, no significant differences were obtained between the emission scenarios. Our review further highlights that changes in land use or soil and water conservation measures can either mitigate (i.e. no tillage, agricultural abandonment, reforestation) or aggravate (i.e. agricultural expansion) the impacts of climate change. This review illustrates that most studies project an increase of soil erosion under future climate change, while environmental (e.g. climate, land use) and methodological (e.g. erosion model, bias-correction, climate ensemble) differences between studies determine the strength and significance of the projected impacts.

We acknowledge funding from the Spanish Ministry of Science, Inovation and Universities (PID2019-109381RB-I00/AEI/10.13039/501100011033).

How to cite: de Vente, J. and Eekhout, J.: The impact of climate change on soil erosion: a systematic review, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5008, https://doi.org/10.5194/egusphere-egu21-5008, 2021.

EGU21-5713 | vPICO presentations | SSS2.7

Selecting suitable climate models for examining future changes in soil erosion

Neil Brannigan, Donal Mullan, Karel Vandaele, Conor Graham, Jennifer McKinley, and John Meneely

Climate models consistently project large increases in the frequency and magnitude of extreme precipitation events in the 21st century, revealing the potential for widespread impacts on various aspects of society. While the impacts on flooding receive particular attention, there is also considerable damage and associated cost for other precipitation driven phenomena, including soil erosion and muddy flooding. Multiple studies have shown that climate change will worsen the impacts of soil erosion and muddy flooding in various regions. These studies typically drive erosion models with a single model or a few models with little justification. A blind approach to climate model selection increases the risk of simulating a narrower range of possible scenarios, limiting vital information for mitigation planning and adaptation. This study provides a comprehensive methodology to efficiently select suitable climate models for simulating soil erosion and muddy flooding. For a case study region in eastern Belgium using the WEPP soil erosion model, we compare the performance of our novel methodology against other model selection methods for a future period (2081 – 2100). The main findings reveal that our novel methodology is successful in generating the widest range of future scenarios from a small number of models, when compared with other ways of selecting climate models. This approach has not previously been achieved for modelling soil erosion by water. Other precipitation-driven impact sectors may also wish to consider applying this method to assess the impact of future climatic changes, so that the worst- and best-case scenarios can be adequately prepared for.

How to cite: Brannigan, N., Mullan, D., Vandaele, K., Graham, C., McKinley, J., and Meneely, J.: Selecting suitable climate models for examining future changes in soil erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5713, https://doi.org/10.5194/egusphere-egu21-5713, 2021.

EGU21-8445 | vPICO presentations | SSS2.7

Assessing the impact of soil erosion on plant vigor (NDVI) and the spatial patterns of soil-bound Cu, Zn and B micro- and N, P macronutrients in a sloping vineyard (Tokaj, Hungary)

Izabella Babcsányi, Ferenc Kovács, Szabolcs Juhász, Péter Balling, Nhung Pham Thi Ha, Zalán Tobak, and Andrea Farsang

Soil erosion in sloping vineyards greatly influence the spatial distribution of soil nutrient contents and can affect plant nutrition and vigor. The study aimed to evaluate possible links between the grapevine (Vitis Vinifera) vigor and the erosion-impacted macro- and micronutrient contents in the topsoil. Our study combined field observations, laboratory measurements and remote sensing data.

The field experiment was performed in a 1.8 ha vineyard plot in Tokaj (NE Hungary) with a mean slope of 8° and a slope length of 270 m. The main soil type in the vineyard is Regosol developed on loess. The stock unearthing method was applied for estimating soil loss/sedimentation in the vineyard. The study plot is separated by pathways perpendicular to the south-facing main slope into four equal areas with decreasing slope steepness. A total of 42 soil samples (0-10 cm) were collected (10-12 in each area) to measure organic matter content, plant-available nitrite+nitrate-N, P2O5-P, and total contents of Cu, Zn and B micronutrients. Additionally, five subsoil samples were taken at 2 m depth for determining micronutrient accumulation in the topsoil due to vine treatments. The spatial variability of topsoil nutrient contents was assessed by interpolating the measured parameters using the inverse distance weighting method. The effects of soil erosion and spatial distribution of the nutrient contents on plant vigor were analyzed using the Normalized Difference Vegetation Index (NDVI). Sentinel-2 images with 10 m resolution were acquired on three dates in June and July 2020. In the study area, a median Cu enrichment factor (EF=topsoil/subsoil) of 2.7 can be attributed to a prevailing anthropogenic origin of the topsoil-bound Cu content. The vineyard is an organic farm, therefore Cu use (in a dose of 4 kg/ha/year) is an obvious way to protect grapevines against fungal infections. We also observed a moderate degree of Zn and B enrichment in the topsoil (EFZn: 1.2, EFB: 1.4) due to vine treatments with foliar fertilizers. The element distribution maps show a fairly similar spatial pattern of Cu, available P2O5-P, and organic matter contents. Their accumulation in the footslope area with the lowest steepness can be seen. Compared with the soil loss/sedimentation map based on stock unearthing data, the Cu, P2O5-P and organic matter contents of the topsoil are lower in areas subject to more intense erosion, which may even affect the development of vines. The latter is to be examined in the light of vegetation indices (NDVI). Changes in vegetation indices along the main slope can be observed with clearly increasing NDVI values in the footslope area. Spatial changes in B, Zn and nitrite-nitrate-N contents do not show a clear relationship with the topographic patterns of the area and the resulting soil erosion losses. Besides the nutrient contents, the presumably higher soil moisture content in the footslope area may also explain the higher NDVI values.

I. B. is grateful for the support of the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences. The research received funds from the OTKA 1K 116981.

How to cite: Babcsányi, I., Kovács, F., Juhász, S., Balling, P., Pham Thi Ha, N., Tobak, Z., and Farsang, A.: Assessing the impact of soil erosion on plant vigor (NDVI) and the spatial patterns of soil-bound Cu, Zn and B micro- and N, P macronutrients in a sloping vineyard (Tokaj, Hungary), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8445, https://doi.org/10.5194/egusphere-egu21-8445, 2021.

EGU21-9182 | vPICO presentations | SSS2.7

Spatio-temporal effects of vegetated windbreaks on wind erosion and microclimate as basis for model development

Thomas Weninger, Simon Scheper, Nathan King, Karl Gartner, Barbara Kitzler, Lenka Lackoova, Peter Strauss, and Kerstin Michel

Wind erosion of arable soil is considered a risk factor for Austrian fields, but direct measurements of soil loss are not available until now. Despite this uncertainty, vegetated windbreaks have been established to minimize adverse wind impacts on arable land. The study addresses these questions: i) How relevant is wind erosion as a factor of soil degradation? ii) How important is the protective effect of vegetated windbreaks? iii) Are systematic patterns of spatial and temporal variability of wind erosion rates detectable in response to weather conditions? 

Two experimental fields adjacent to windbreaks were equipped with sediment traps, soil moisture sensors, and meteorological measurement equipment for microclimatic patterns. Sediment traps were arranged in high spatial resolution from next to the windbreak to a distance of ten times the windbreak height. Beginning in January 2020, the amount of trapped sediment was analyzed every three weeks. The highest wind erosion rates on bare soil were observed in June and July. For unprotected fields with bare soil, upscaled annual erosion rates were as high as 0.8 tons per hectare, and sediment trapped increased in a linear fashion with distance from the windbreak. Soil water content near the surface (5 cm depth) was three percent higher at a distance of two times the height of the windbreak than at a distance of six times the height. For the same respective distances from the windbreak, we observed 29 days of soil water contents below the wilting point compared with 60 days.

The preliminary outcomes confirmed the expected effects of windbreaks on soil erosion and microclimate in agricultural fields. Prospective results from multiple vegetation periods will be used in an upscaling approach to gain informations for the whole basin. That is meant to be done by a combination with a soil wind erosion model which was so far used for regional modelling of wind erosion susceptibility.

How to cite: Weninger, T., Scheper, S., King, N., Gartner, K., Kitzler, B., Lackoova, L., Strauss, P., and Michel, K.: Spatio-temporal effects of vegetated windbreaks on wind erosion and microclimate as basis for model development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9182, https://doi.org/10.5194/egusphere-egu21-9182, 2021.

EGU21-9544 | vPICO presentations | SSS2.7

The short-term effects of bench terrace construction for planting eucalypt trees on soil fertility

Martinho A S Martins, Ana I Machado, Adriana Xavier, Ana R Lopes, Bruna R F Oliveira, Liliana B Simões, Svenja van Schelve, Nelson Abrantes, and Jan Jacob Keizer

In recent decades, the establishment of monospecific tree plantations has increased markedly. Such changes in land use may have important implications for soil properties and functions. At present, the most common monospecific tree plantations worldwide are those of eucalypt, and they have been reported to negatively affect soil functions such as carbon sequestration and soil biodiversity (macroinvertebrates). This has been attributed, at least in part, to the practice of soil mobilization prior to tree planting. Arguably, the construction of bench terraces for installing eucalypt plantation is an extreme form of soil mobilization and has become increasingly common in Central Portugal, including to facilitate forestry operations on steep slopes such as the planting itself, the application of agrichemicals for fertilization and weed control, mechanical control of the understory fuel load, and the logging and extraction of wood. While bench terracing is a technique that aims at soil and water conservation on steep slopes that are otherwise very hard to cultivate, its effectiveness has been poorly studied. Considerable rates of splash erosion have been reported on the terraces themselves during the initial period after their construction, and so have elevates rates of water erosion on steep tracks.  Slope-scale soil losses, however, are difficult to quantify, even using erosion survey methods due to the fast growth of the eucalypts. While the same is true for the associated fertility losses, the main impact of bench terracing on topsoil fertility may results from the - massive -redistribution and inversion of the soil layers up to depths of 30 cm and more. This study aimed to quantify this direct effect of bench terracing on soil nutrient status. To this end, a 10 ha forest land property was sampled before and immediately after bench terracing during summer 2019. Before bench terracing, on 4th of April 2019, soil sampling was carried out at 5 points along a transect of 100 m centred on the middle section of a South-East facing slope; after bench terracing, on 23rd July 2019, soil sampling was carried out on 5 terraces on the same slope section, separated from each other by 1 terrace. Before bench terracing, the O layer, and the 0-10 cm (A horizon) and 15-20 (B horizon) mineral soil depths were sampled at each transect point; after terracing, the 0-20 cm of mixed mineral soil depths were sampled at each terrace. The mineral soil samples were analysed with respect to PMN and HCW as well as total C, N and P. The results showed clear differences between the nutrient status of the mineral soils before and after bench terracing. The construction of bench terraces diminished all soil nutrient analysed, this not only affected the stock of soil major nutrients, but also strongly affect the labile and plant available fractions. Therefore, terracing has immediately implications in soil fertility and may impose important limitations in the kye ecological functions of forest soil such as nutrient cycling, storage and turnover.

How to cite: Martins, M. A. S., Machado, A. I., Xavier, A., Lopes, A. R., Oliveira, B. R. F., Simões, L. B., Schelve, S. V., Abrantes, N., and Keizer, J. J.: The short-term effects of bench terrace construction for planting eucalypt trees on soil fertility, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9544, https://doi.org/10.5194/egusphere-egu21-9544, 2021.

EGU21-9717 | vPICO presentations | SSS2.7

Erodibility of loess depending on its weathering: field experiments

Jan Vojtisek and Jiri Bruthans

Piping is an erosion process in which cracks and macropores extend into channels with a diameter of cm or more. The study of loess erosion is important because loess covers about ten percent of the continents surface and is susceptible to piping, formation of gullies and intense erosion of agricultural soil. Study was done in Střeleč quarry (Czech Republic), where a several meters thick loess cover occurs in the upper part, sometimes with cracks and macropores. Rill erosion and piping conduits are formed in the loess cover and this makes it an ideal place for field experiments and observations. The erosion rate of the loess by water trickle at quarry face, erosion of the drill hole and erosion under the impact of the droplets were studied. The erosion rate of the rills was measured using long screws screwed directly into the rill. Rapid erosion occurred within first tens of centimeters from original ground surface in the zone where the loess structure was disintegrated by frost or wetting-drying cycles. Below this zone, the erosion rate was much lower, and it ceased with time as rill deepened. Small piping conduits developed rapidly by pouring water into small desiccation cracks on the loess surface. On the other hand, the dril hole did not expand into piping conduit in deeper zone of loess. Moisture content of small loess blocks have strong impact on final degree of erosion. While dry blocks began to disintegrate relatively quickly into incoherent material, the pre-wetted samples did not disintegrated and more or less kept their initial shape. This shows that slaking is responsible for disintegration of small dry blocks on loess surface. While the surface zone of the loess is highly erodible by flowing water, probably due to the loss of its original structure, the loess in the deeper zone is far less erodible in the quarry and even pre-formed conduit (dril hole) do not develop into larger conduit.

 

Many thanks to the management of Střeleč Quarry for enabling of the field documentation and experiments. The research was supported by Charles University Grant Agency (GAUK #1292119).

How to cite: Vojtisek, J. and Bruthans, J.: Erodibility of loess depending on its weathering: field experiments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9717, https://doi.org/10.5194/egusphere-egu21-9717, 2021.

EGU21-10087 | vPICO presentations | SSS2.7 | Highlight

Modelling event scale rainfall erosivity across European climate regions 

Francis Matthews, Panos Panagos, and Gert Verstraeten

The characteristics (magnitude and timing) of individual rainfall erosivity (RE) events in Europe strongly control soil loss at timescales from the individual event to long term annual average. While annual averages of soil erosion encompass the long-term variability of the event-based drivers of soil erosion (soil condition, water kinetic energy, vegetation properties), they provide both little direct information on the timing of soil loss or capacity to fully understand future erosion. Across the spectrum of empirical to physically based process models, event-scale estimates of rainfall energy are vital. The (R)USLE EI30 index is a popular description of the combined effect of rainfall kinetic energy and the maximum 30-minute intensity of a rainfall event on soil loss. Modelling RE from daily or event rainfall accumulation seeks to capture the intra-annual meteorological controls on the EI30 index, with the goal of utilising rainfall data with higher abundance (eg daily) than conventional but less common hyetograph data. To date, no systematic study has provided model parameter surfaces for Europe’s climatic regions and investigated their spatial configuration. For each of 74 relevant environmental strata (EnS) within 13 broader environmental zones, we calibrate and validate 5 power-law based models with monthly and annual parameter sets using the REDES dataset, composed of over 300,000 RE events from national gauge networks.

We demonstrate the applicability of delineated environmental strata for subsampling and modelling event rainfall erosivity with heterogeneous national gauge data coverage and extent. Power-law model fits with 12 individual monthly parameter sets outperformed annual models with periodic cosine functions. The power-law α and β parameters are generally correlated through space (r = 0.66) and follow the general European trend of long-term annual average RE, increasing from North-West to South-East. The average annual Nash-Sutcliffe model efficiency for all strata increased from 0.427 (max: 0.76, min: 0.21) to 0.437 when the top 1 percentile of events were removed, which contribute between 8 and 27% of the total RE per stratum. The prediction capacity was higher in autumn and winter than in spring and summer when rainfall holds generally higher unit kinetic energy. Average model efficiency per environmental zone depended on both the rainfall stochasticity and size of the national data sample within each stratum, highlighting the importance of ample data extents for predicting event rainfall erosivity in Europe.

How to cite: Matthews, F., Panagos, P., and Verstraeten, G.: Modelling event scale rainfall erosivity across European climate regions , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10087, https://doi.org/10.5194/egusphere-egu21-10087, 2021.

Fuzzy logic is often used for calculation and simulation of real environmental situations. Wind erosion can often be complex, and from various erosion situations it is one of the hardest to be calculated and exactly described. In our research, we based the structure of the fuzzy system on the soil loss of six soils with different mechanical compositions measured in wind channels. Measurement of soil loss in four wind speed ranges during soil channel testing of soils. During the wind tunnel analysis of the soils, the topsoil loss was measured in four wind speed ranges (I. 11,2-11,6 m/s; II. 12.5-13.3 m/s, III. 14.4-14.7 m/s, IV. 15.5-15.7 m/s) on six soils with different mechanical compositions (four sand and two clayey sand soil). The mathematical model programmed and built up in MATLAB, this mamdani type fuzzy evaluation system uses two input parameters wind speed and ErosionFactor. The mathematical model requests the soils mechanical composition and identifies it based on the USDA triangle diagram. Many mathematical methods applicable to fine tune a fuzzy system. We have chosen the method of exhaustive design to cover the whole parameter space. The mathematical model calculated the soil loss. Model runs were also performed with the SWEEP model according to the soils examined in the wind tunnel. Based on our results, we found that using our fuzzy mathematical model, we obtained estimated soil loss values similar to the SWEEP model compared to the soil loss measured in the wind tunnel. However, it should be noted that the USDA SWEEP model requires a much larger amount of data to estimate the extent of soil loss caused by a wind erosion damage event.

How to cite: Tatárvári, K. and Piros, A.: Fuzzy mathematical model for estimating wind erosion based on wind tunnel data, comparison of results with laboratory measured and SWEEP model results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13701, https://doi.org/10.5194/egusphere-egu21-13701, 2021.

EGU21-1432 | vPICO presentations | SSS2.7

A Rainfall Erosivity database for Brazil from MSWEP rainfall dataset

Ingrid Petry and Fernando Mainardi Fan

In erosion studies the behavior of rainfall is primordial, since rain is responsible for the first stage of the erosion process: the detachment of soil particles. The erosive potential of rainfall, erosivity, is considered in the universal soil loss equations (R)USLE family through the parameter R, or R factor. This factor is calculated from the rainfall erosivity index, which is the product of kinetic energy of the rain by the maximum intensity of the rain of 30 minutes of duration. As sub-hour rainfall data is not always available, there are in the literature a series of equations obtained from regression, which use monthly and annual rainfall and present a good estimate of erosivity for your study site. In Brazil, in addition to limitations regarding the temporal resolution of rainfall data, there are also spatial limitations. Monitoring stations are concentrated mostly in urbanized areas, usually near the coast. The other regions, such as agricultural and forest areas, are poorly monitored, and these areas are of great interest for monitoring erosion, not only because they are periodically exposed soil areas, but also because of the high rainfall rates that humid forests like Amazon have. MSWEP is a rainfall database that combines observed, satellite and reanalysis data. It has global coverage, temporal resolution of 3 hours, spatial 0.1º and data from 1979 to 2016. Databases like this have great potential to be used in areas such as Brazil, due to its spatial and temporal resolution. In this context, considering the relevance that the soil loss equations still present today, this work developed a rainfall erosivity database entitled REDB-BR (Rainfall Erosivity Database for Brazil). It provides the R factor in a 0.1º resolution grid, developed with 37 years of rainfall data from the MSWEP dataset. The R factor was calculated trough 73 erosivity index regression equations, which mostly uses the Modified Fournier Index (MFI), a relation between monthly precipitation and annual precipitation. Thiessen polygons were used in order to spatialize and define the areas of each equation. Over the Brazilian territory, the R factor ranges from 1.200 to 20.000 MJ mm ha-1 h-1 year-1, with the higher values in the North region, and the lowest values in the Northeast. The spatial patterns of erosivity are very similar to the climatic zones of Brazil. The R factor map takes advantage of MSWEP dataset and presents a spatial resolution very detailed to a country with continental scale such as Brazil. The database includes the equations shapefile and table, Thiessen Polygons shapefile and the R factor map in raster format, which allows more possibilities of application. The database can be accessed at <https://zenodo.org/record/4428308#.X_hxsOhKiUk>. We identified sudden changes in behavior between the delimited areas, which suggests a need for more regression equations in order to better represent the behavior of the erosivity in the Brazilian territory.

How to cite: Petry, I. and Mainardi Fan, F.: A Rainfall Erosivity database for Brazil from MSWEP rainfall dataset, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1432, https://doi.org/10.5194/egusphere-egu21-1432, 2021.

EGU21-14186 | vPICO presentations | SSS2.7

The analysis of splash erosion depending on the degree of soil wettability - a preliminary study

Agata Sochan, Rafał Mazur, Michał Beczek, Magdalena Ryżak, Cezary Polakowski, and Andrzej Bieganowski

The soil splash phenomenon is the initial stage of the water erosion process. It occurs when a rain drop hits the soil surface and causes a few processes e.g. i) detachment of soil particles and their transport over different distances, ii) breakdown of soil aggregates, iii) surface runoff or iv) formation of a crusted surface.

The aim of the study was to carry out an analysis of the splash erosion in mineral soil in 4 variants of sample preparation: a) dry natural soil, b) wet natural soil, c) dry burnt soil, d) wet burnt soil.

In both cases (natural soil and soil modified with high temperature), full moistening was achieved by capillary rise. Fire simulation was carried out in several variants at varying temperature and duration. Variant that affected soil wettability to the greatest extent was selected for the splash analyses. "Natural" and "modified" wettability were measured using the water drop penetration time (WDPT) method. "Natural" wettability classified soil into the "wettable" group (WDPT < 5s), while the modification of the surface properties by high temperature changed the wettability group of the analyzed soil into "slightly to moderately repellent" (5 s > WDPT < 60s).

Each time, the soil material was placed in aluminum rings with an internal diameter of 36mm and a height of 10mm, and the surface was leveled without excessive compaction of the sample.

A single drop of distilled water with a diameter of 4.2 mm fell on the sample prepared in this way from a height of 1.5m. The drops were dosed with a peristaltic pump and reached the final velocity of 4.98 m/s.

Three synchronized Phantom Miro M310 cameras (Vision Research, USA) were used to register the splash phenomenon. The recorded films were used to analyze the splash phenomenon through measurements of the velocity, angle and distance of ejected particles.

A Scan3D UNIVERSE 10 MPiX structural light scanner (Smarttech 3d, Poland) was used to determine the magnitude of the surface deformation caused by the drops. The analyses made it possible to determine e.g. the depth, diameter, and volume of craters and the height of surrounding rims.

The analysis of the results showed significant differences in the size and dynamics of the emerging splash depending on the degree of soil wettability.

The study was partially funded by the National Science Centre, Poland, as part of project no. 2017/26/D/ST10/01026.

How to cite: Sochan, A., Mazur, R., Beczek, M., Ryżak, M., Polakowski, C., and Bieganowski, A.: The analysis of splash erosion depending on the degree of soil wettability - a preliminary study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14186, https://doi.org/10.5194/egusphere-egu21-14186, 2021.

SSS2.10 – Impacts of natural and anthropogenic disturbances on water and sediment connectivity at multiple scales

EGU21-7643 | vPICO presentations | SSS2.10

Assessing the effect of the Vaia storm on sediment source areas and connectivity storm in the Liera catchment (Dolomites)

Gabriella Boretto, Stefano Crema, Lorenzo Marchi, Giovanni Monegato, Luciano Arziliero, and Marco Cavalli

Extreme meteorological events are important causes of environmental damages, particularly in mountain areas that can be heavily affected by destructive processes such as landslides and debris flows. From 27 and 30 October 2018, an extraordinary storm - named Vaia - hit Northeastern Italy. The Vaia storm triggered mass wasting processes, generated new slope instabilities, caused widespread windthrows, and damaged human infrastructure. This work aims at assessing the effect of the Vaia storm in the Liera Torrent basin (Venetian Dolomites, Italy), by building and comparing sediment source inventories before and after the Vaia storm. The Liera basin drains an area of 35 km2 and elevation ranges between 976 and 3192 m a.s.l. The mapping and classification of the sediment sources have been carried out through the interpretation of high-resolution orthophotos and Digital Terrain Models (DTMs) derived from airborne LiDAR data (1-m resolution) acquired in 2015 and 2019. A topography-based index of sediment connectivity has been applied to characterize connectivity spatial patterns at catchment scale and identifying the sediment sources on the hillslopes effectively connected to the Liera torrent. A preliminary connectivity analysis showed that the upstream sector the catchment located in the Pale di San Martino plateau is not effectively connected to the lower Liera valley because of its karstic environment and debris originated from the highest portion of the relief are confined in a hollow. Thus the inventories have been limited to the medium and lower parts of the catchment considering an area of 20 km2. Results indicated a total of 1650 sediment source areas after the Vaia event, with an areal increase of about 20% with respect to 2015 inventory, especially due to the development of landslide (843 in total for the 2019 inventory), expansion of the debris flow channel (257) and areas subject to surficial erosion (127). Other areas that have been identified encompass debris flow deposit (288), rock fall deposit (31), stream bank erosion (45), and other sediment source areas which need field survey to be properly classified (59). The analysis allowed: (1) obtaining reliable and detailed pre- and post- event sediment sources inventories, (2) assessing sediment connectivity at the catchment scale, which is fundamental for estimating the contribution of sediment sources and related transfer paths, (3) improving sediment dynamics understanding related to the Vaia storm in the study area. Future analysis will focus on field validation and residual sediment availability for the investigated areas. This study was carried out in the frame of the Interreg V-A Italy - Austria SedInOut project.

How to cite: Boretto, G., Crema, S., Marchi, L., Monegato, G., Arziliero, L., and Cavalli, M.: Assessing the effect of the Vaia storm on sediment source areas and connectivity storm in the Liera catchment (Dolomites), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7643, https://doi.org/10.5194/egusphere-egu21-7643, 2021.

EGU21-7587 | vPICO presentations | SSS2.10

Anthropogenic impact on urban rivers: insights from the Mugnone Creek (Florence, Italy) waters and sediments characterization in the framework of the multidisciplinary SENECA project

Gabriele Bicocchi, Stefania Venturi, Alessio Monnanni, Tania Martellini, David Chelazzi, Eleonora De Beni, Alessandra Cincinelli, Guia Morelli, Pierfranco Lattanzi, Silvia Fornasaro, Francesco Ciani, Pilario Costagliola, and Valentina Rimondi

Urbanization is a striking phenomenon, responsible for the development of cities as complex and highly dynamic systems. One of the most pressing issues in urban areas is water cycle management, which directly influences the availability and the quality of this resource. Urban streams are highly vulnerable to the impacts resulting from the increasing urbanization and they have often lost most of their pristine, natural character.

We hereby present the preliminary results of the multidisciplinary StrEams urbaN Ecological City plAnning (SENECA) project, which is not only but mainly devoted to characterizing the chemical features of stream waters and sediments of the Mugnone Creek (MC). MC is a typical example of an urban stream, crossing the city of Florence (Italy) and eventually discharging to the Arno River, that has suffered an intense denaturation due to the urban sprawl, such as several diversions, canalizations and rectifications, alterations of the stream bed and riparian habitat, widespread concrete revetment of the banks and burial of short stream tracts.

Different sites along the 17-km long MC were investigated for water and sediment geochemistry from upstream of the Florence urban area (“blank” sites) to the MC outlet (Cascine Park), passing through variably urban-impacted areas, including sites located along traffic-congested roads, close to the new tramway construction sites and under the railway line. Stream waters were sampled twice a year (June and December 2019 and 2020) to account for seasonal variability. Stream discharge at three representative points was simultaneously determined during water sampling to allow mass load calculations of contaminants. In details, major dissolved ions (Ca, Mg, Na, K, HCO3, SO4, Cl, NO3) and reduced nitrogen (NH4), trace elements (TEs: Sb, As, Cu, Zn, Cd, Co, Ba, Li, Pb, Ni) and microplastics (MPs) in stream sediments and waters of MC were determined. Major dissolved ions and NH4 were analysed via acidimetric titration and IC. TEs were determined in both sediments and waters (0.45 μm filtered and unfiltered) by ICP-OES and ICP-MS, respectively. MPs (1 μm-5 mm) were identified in sediments and waters by HD binocular stereomicroscope.

Chemical composition (major element constituents) of water reflected both the seasonality and the progress of the water-rock interaction acting in MC from its spring toward the outlet. In addition, the pattern of abundances of Cu, Zn, Sb and Pb and especially their mass loads reflect the increasing anthropogenic impact on the water and sediments, even if is important to stress that the contents are within the limits defined by law, except for stream sediments at a few sites. For MPs, up to 109 particles, coming mainly from the NW side of Florence, are estimated to be discharged daily to the Arno River during the winter season, much higher than creeks with similar urbanization contexts worldwide. Increasing data collection will make it possible to identify and better understand what type of sources and processes are responsible for the anthropogenic impacts in the MC and could help in better safeguarding the creek within the framework of the urban social-ecological systems of Florence.

How to cite: Bicocchi, G., Venturi, S., Monnanni, A., Martellini, T., Chelazzi, D., De Beni, E., Cincinelli, A., Morelli, G., Lattanzi, P., Fornasaro, S., Ciani, F., Costagliola, P., and Rimondi, V.: Anthropogenic impact on urban rivers: insights from the Mugnone Creek (Florence, Italy) waters and sediments characterization in the framework of the multidisciplinary SENECA project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7587, https://doi.org/10.5194/egusphere-egu21-7587, 2021.

EGU21-403 | vPICO presentations | SSS2.10

A new method to evaluate the accuracy of the sediment source mixing model

Peng Shi, Yang Yu, Lulu Bai, and Peng Li

Fingerprint identification technology has been widely used to extract sediment source proportions, but the only indicator currently available to assess the accuracy and applicability of the results is good-fit (GOF). We have proposed a new method to evaluate sediment source results and quantitatively evaluate the applicability of sediment source mixing models. A typical check dam in the Loess Plateau was used to evaluate the new method by combining field sampling and numerical simulations. Collins (C) and modified Hughes mixing (M-H) models were used to quantitatively analyze the sediment sources of the check dams built and operated until July 2017. The results showed that the best combination for the fingerprint factors in the dam-controlled watershed, was Zn, Mg, Mn, and d (0,1), which had an 86.1% identification ability. With rainfall, the relative sediment contribution rates from gullies, sloping farmland, grasslands, and branch ditches were 54.22%, 23.56%, 15.54%, and 6.68%, respectively. The M-H mixing model had a higher comprehensive score (2.72) when compared with the C mixing model (2.54). The comprehensive evaluation method could provide an effective scientific theoretical basis for optimal allocations of water and soil conservation in small watersheds.

How to cite: Shi, P., Yu, Y., Bai, L., and Li, P.: A new method to evaluate the accuracy of the sediment source mixing model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-403, https://doi.org/10.5194/egusphere-egu21-403, 2021.

EGU21-5245 | vPICO presentations | SSS2.10

Impact of a volcanic eruption on the sediment connectivity of a Chilean river basin: the Calbuco study case

Marco Andreoli, Lorenzo Martini, Marco Cavalli, Andrés Iroumé, and Lorenzo Picco

Volcanic eruptions are natural disturbances capable of introducing large quantities of sediment into river systems as to upset the transport regime for several years. Such a disturbance can have a strong impact on the water and sediment flows and consequently on the transport capacity. Moreover, changes in morphological settings and land cover lead to an alteration of the sediment connectivity within the catchment. This study aims to investigate the changes of sediment connectivity in a catchment affected by an explosive volcanic eruption using the Index of Connectivity (IC) with a multi-temporal approach. Potential variations were analyzed at the catchment scale over a period of 6 years, before and after the eruption. The study area, located in southern Chile, is the Blanco Este River basin (39,6 km²), affected by the eruption of the Calbuco volcano (April 2015, total volume of sediment expelled of about 0,28 km³) which profoundly changed its vegetation cover, geomorphology and hydrology. IC analyses were based on low-resolution and freely available data (i.e., GDEM, Landsat 8 satellite images). Through supervised image classification and field data survey, a Manning's n coefficient for overland flow is derived as weighting factor (W) due to its suitability to represent the impedance to sediment flows in catchments characterized by land cover variations. Following the eruption, bare soil cover on the basin doubled (from 5% to 10% of total basin area). Consequently, the multi-temporal analysis results in an overall increase of IC with the median value ranges from -3,58 to -3,26 in pre-eruptive (2015) and first post-eruptive scenario (2016), respectively. The connectivity maps show that the higher IC values (i.e. range from -1,23 to 1,66) are persistently located in three areas: at the base of the volcanic dome, on the steepest slopes near the main channel and in a sub-basin on the right side of the catchment. Moreover, the Difference of IC (DoIC) among different scenarios highlighted the major variations. Such changes are found along the volcano slopes, in a flat area located in the upper part of the basin and along the lower valley of the Rio Blanco Este. The study proposes a useful methodology to evaluate the sediment connectivity, and its evolutionary trends, in environments affected volcanic eruptions starting from low-resolution data and field survey. These results may help to better define types, location and typologies of interventions to improve the river management approaches, considering the ongoing cascading processes. This research is funded by the Fondecyt 1200079 project.

How to cite: Andreoli, M., Martini, L., Cavalli, M., Iroumé, A., and Picco, L.: Impact of a volcanic eruption on the sediment connectivity of a Chilean river basin: the Calbuco study case, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5245, https://doi.org/10.5194/egusphere-egu21-5245, 2021.

EGU21-562 | vPICO presentations | SSS2.10

A model-based sediment connectivity assessment for patchy agricultural catchments

Pedro Velloso Gomes Batista, Peter Fiener, Simon Scheper, and Christine Alewell

Sediment connectivity is highly influenced by landscape patchiness. In particular, linear features such as roads, ditches, and terraces, modify landscape patterns and affect sediment transport from hillslopes to surface waters. Connectivity patterns are commonly assessed by spatially-distributed models, which rely on semi-qualitative indices or numerical simulations of soil erosion and sediment transport. However, model-based connectivity assessments are hindered by the uncertainty in model structure and parameter estimation. Moreover, representing linear landscape features is often limited by the spatial resolution of the model input data. Here we demonstrate how a global sensitivity analysis of the WaTEM/SEDEM model can be used to improve our understanding of sediment connectivity in patchy agricultural catchments of the Swiss Plateau. Specifically, we explored model structural connectivity assumptions regarding road drainage and the presence of edge-of-field buffer strips, as well as the uncertainty in the input data, by means of a Monte Carlo simulation and a high resolution 2 m x 2 m DEM. Our results showed that roads are the main regulators of sediment connectivity in ameliorated Swiss landscapes. That is, our sensitivity analysis revealed that assumptions about how the road network (dis)connects sediment transport from cropland to water courses had a much higher impact on modelled sediment loads than the uncertainty in model parameters. These results illustrate how a high-density road network combined with an effective drainage system increases sediment connectivity from arable land to surface waters in Switzerland. Additionally, our approach underlines the usefulness of sensitivity and uncertainty analysis for identifying relevant processes in model-based sediment connectivity assessments.

How to cite: Velloso Gomes Batista, P., Fiener, P., Scheper, S., and Alewell, C.: A model-based sediment connectivity assessment for patchy agricultural catchments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-562, https://doi.org/10.5194/egusphere-egu21-562, 2021.

Preferential flow (PF)-dominated soil structure is often considered a unique system consisting of micropores and macropores and thus supposed to provide dual-pore filtering effects on hydrological signals, through which smoothing effects are likely to be stronger for matrix flow and weaker for PF via macropores. By using time series of hydrological signals (precipitation, canopy interception, throughfall, soil moisture, evapotranspiration, water storage in soil and groundwater, and catchment discharge) propagating through the Shale Hills Catchments and representative soil series, the filtering effects of the catchment and soil profiles were tested through the wavelet analysis. The hypothesized dual-pore-style filtering effects of the soil profile were also confirmed through the coherence spectra and phase differences, rendering them applicable for possible use as “fingerprints” of PF to infer subsurface flow features. We found that PF dominates the catchment’s discharge response at the scales from three to twelve days, which contributes to the catchment discharge mainly as subsurface lateral flow at upper or middle soil horizons. Through subsurface PF pathways, even the hilltop is likely hydrologically connected to the valley floor, building connections with or making contributions to the catchment discharge. This work highlights the potential of wavelet analysis for retrieving and characterizing subsurface flow processes based on the revealed dual-pore filtering effects of the soil system.

How to cite: Liu, H., Zhao, W., Yu, Y., Guo, L., and Liu, J.: Subsurface Preferential Flow Enhances Hydrological Connectivity in the Shale Hills Catchment: Perspective from Wavelet-based Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2427, https://doi.org/10.5194/egusphere-egu21-2427, 2021.

In semi-arid ecosystems, basin elevation and hillslope aspect play an important role in the distribution of plant type and density. In general, north-facing aspects host mesic and denser vegetation than south-facing aspects where host xeric plants. Beside aspect, elevation plays a dominant role in vegetation distribution. The Upper Rio Salado Basin, in central New Mexico, hosts shrublands and grasslands at lower elevations and forests at higher elevations. The geomorphometric analysis shows that forest areas are steeper than the grasslands and shrublands. Shrub encroachment in the region and the increase in global temperatures may lead to the replacement of forests by shrublands and the transition from a resource-conserving ecosystem to a leaky (non-conserving) ecosystem on the north-facing aspects which is similar to current south-facing aspects. The preliminary results show these transitions will lead to emerging hotspot areas in erosion. These erosion­-prone zones should be monitored in future for sustainable management.

This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not mean that the content of the publication is approved in a scientific sense by TUBITAK.

How to cite: Yetemen, O.: Implications of Climate Change on Erosion Dynamics and Sediment Connectivity in Semi-arid Ecosystem, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14482, https://doi.org/10.5194/egusphere-egu21-14482, 2021.

EGU21-13758 | vPICO presentations | SSS2.10

Effect of ecological construction on sediment connectivity in a typical small watershed on Loess Plateau

Yongyong Ma, Zhanbin Li, Jingming Hou, Peng Li, Zongping Ren, and Kexin Lu

In recent years, the significantly decrease of water and sediment in the Yellow River has attracted wide attention from domestic and foreign scholars. The Loess Plateau is the main source of sediment in the Yellow River, which ecological environment changes caused by large-scale ecological construction measures is considered as one of the main factors affecting the water and sediment changes in the Yellow River. In this study, the Wangmaogou small watershed in Loess Plateau was taken as the study area. On the basis of summing up the process of ecological construction in Wangmaogou watershed, and restoring the topography before ecological construction by topographic map, we set up four scenarios of ecological construction to analyzed the characteristics of sediment connectivity under different ecological construction scenarios and the effects of ecological construction on sediment connectivity, which are before ecological construction, only slope measures are built, only channel measures are constructed, and at the same time slope measures and channel measures are constructed. Under the same ecological construction scenario, the index of sediment connectivity (IC) of the basin shows a decreasing trend from ridge to gully, which mean the connectivity of the sediment at the ridge is less than that at the gully, and the gully are more prone to occur soil erosion than ridge. The distributed of large amount of construction land in the middle and lower reaches at the main gully of Wangmaogou small watershed reduces the connectivity of their surrounding sediment, and the region is prone to occur sediment deposition. Eco-construction measures have decreased significantly the sediment connectivity index (p<0.01) of Wangmaogou small watershed, and reduced the occurrence of soil erosion. Laying ecological measures lessened the possibility of local soil erosion, and increased the resistance of sediment in the transport process. Compared with the situation without ecological control, the mean of Dup index decreased by 75.27% by laying slope and gully measures, while the mean of Dup index decreased by only 6.45% by laying gully measures.

How to cite: Ma, Y., Li, Z., Hou, J., Li, P., Ren, Z., and Lu, K.: Effect of ecological construction on sediment connectivity in a typical small watershed on Loess Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13758, https://doi.org/10.5194/egusphere-egu21-13758, 2021.

EGU21-12904 | vPICO presentations | SSS2.10

Structural, Hydrologic, and Sediment Connectivity in a Shrub-Encroached and Restored Semiarid Grassland

Justin Johnson, Jason Williams, Phillip Guertin, Steven Archer, Philip Heilman, Frederick Pierson, and Haiyan Wei

Shrub encroachment of semiarid grasslands is influenced by connected runoff and erosion patterns that preferentially accumulate resources under vegetated patches (canopy microsites) and deplete interspaces. Soil loss from dryland hillslopes results when areas of bare ground become structurally and functionally connected through overland flow. Although these patterns have been well-described, uncertainty remains regarding how these feedbacks respond to restoration practices. This study compared the structure and hydrologic function of a shrub-encroached semiarid grassland treated five years prior with the herbicide, tebuthiuron, to that of an adjacent untreated grassland. Through a series of hydrologic experiments conducted at increasing spatial scales, vegetation and soil structural patterns were related to runoff and erosion responses. At a fine scale (0.5 m2), rainfall simulations (120 mm·h-1 rainfall intensity; 45 min) showed herbicided shrub canopy microsites had greater infiltration capacities (105 and 71 mm·h-1 terminal infiltration rates) and were less susceptible to splash-sheet erosion (3 and 26 g sediment yield) than untreated shrub canopy microsites, while interspaces were statistically comparable between study sites. Concentrated flow simulations at a coarse scale (~9 m2) revealed that gaps between the bases of vegetation (i.e. basal gaps) > 2 mwere positively related to both concentrated flow runoff (r = 0.72, p = 0.008) and sediment yield (r = 0.70, p = 0.012). Modeled hillslope-scale (50 m2) runoff and erosion (120 mm·h-1 rainfall intensity; 45 min) indicated less soil loss in the tebuthiuron-treated site (1.78 Mg·ha-1 tebuthiuron; 3.19 Mg·ha-1 untreated), even though runoff was similar between sites. Our results suggest interspaces in shrub-encroached grasslands continue to be runoff sources following herbicide-induced shrub mortality and may be indicators of runoff responses at larger spatial scales. In contrast, sediment sources are limited post-treatment due to lesser sediment detachment from sheet-splash and concentrated flow processes. Reduced sediment supplies provide evidence that connectivity feedbacks that sustain a shrub-dominant ecological state may have been dampened post-treatment. Our study also highlights the utility of simple measures of structural connectivity, such as basal gaps, as an indicator of hillslope susceptibility to increased runoff and erosion.

How to cite: Johnson, J., Williams, J., Guertin, P., Archer, S., Heilman, P., Pierson, F., and Wei, H.: Structural, Hydrologic, and Sediment Connectivity in a Shrub-Encroached and Restored Semiarid Grassland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12904, https://doi.org/10.5194/egusphere-egu21-12904, 2021.

EGU21-13725 | vPICO presentations | SSS2.10

Investagation of the sediment connectivity under freeze-thaw meltwater compound erosion condition on loessal slope

Tian Wang, Peng Li, Jingming Hou, Zhanbin Li, Shengdong Cheng, and Feng Wang

The connectivity of rill erosion and overland flow are significantly affected by freeze-thaw cycles. Meltwater concentrated flow laboratory experiments were carried out to assess the soil erosion connectivity of different frozen conditions based on simplified hydrological curve and relative surface connection function. The experiments were performed over frozen, shallow-thawed, and unfrozen soil-filled flumes under 1, 2, and 4 L/min flow rates with the temperature around 5 °C. The results imply that according to the spatial distribution of the high connected areas on the slope, the connectivity of the sediment structure on the slope is obviously enhanced with the increase of the flow rate. The order of the structural connectivity of the sediment on the slope with different freeze-thaw states under the same flow rate is: frozen slope > shallow-thawed slope > unfrozen slope. Under different flows and soil frozen conditions, the laws of the vertical and horizontal connectivity rates of the slope are relatively similar which increase first and then stabilize, while the horizontal connectivity rate first decreases and then stabilizes. From the perspective of horizontal connectivity, the erosion form at the beginning of the experiment was mainly surface erosion; as the experiment progressed, the erosion form gradually changed from surface erosion to rill erosion. The results of this research would provide specific implications about meltwater erosion connectivity for improving the erosion process understand.

How to cite: Wang, T., Li, P., Hou, J., Li, Z., Cheng, S., and Wang, F.: Investagation of the sediment connectivity under freeze-thaw meltwater compound erosion condition on loessal slope, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13725, https://doi.org/10.5194/egusphere-egu21-13725, 2021.

The soils are susceptible to water erosion in the hilly and ravine region of the Loess Plateau due to the readily erodible attribute of soils, erosive geomorphology, land use and land cover, and erosive rainfall. The soil and water losses induced by water erosion have the significant on-site impacts on crop growths and yields in this region because of soil nutrient depletion and adverse soil moisture condition. In addition, the crops grown in different land types frequently suffer from the seasonal draught due to climate change, which leads to the decline or failure of crop yield. Therefore, the crop yields and grain production are susceptibly stressed by soil erosion and drought in this region. Soil erosion and draught are the essential issues faced by agriculture production and eco-environment. Alternatively, effective measures of soil and water conservation can incredibly control soil and water losses induced by water erosion, alleviate the influences of draught on crop yields, and sustain grain production in this region. The check dam is one of the widely adopted engineering measures of soil and water conservation in the valleys of the hilly and ravine region on the Loess Plateau. Check dam can play multiple roles in mitigating soil erosion, trapping eroded sediments, regulating runoff and creating the lands in the valleys in the context of water erosion. The check dam can control the soil erosion to some extent because it can raise the basis level of erosion in the valley. The lost sediment and runoff can be trapped by the check dam in a watershed, which can reduce resultant loss rate of soil and water in the outlet of the watershed and mitigate sediment loads in the rive connecting to the watershed. Moreover, the check dam can make sediments or eroded soils deposit so as to develop the relatively flat lands called as the dam-trapped farmland in the valleys. The dam-trapped farmlands along with the terrace lands are regarded as the crucial farmlands due to their excellent farming conditions in this region. Some grain crops, such corn, sorghum, millet or potato, are always grown in the dam-trapped farmlands, among which corn is frequently planted in this kind of farmland. The crop yields of the dam-trapped farmlands have been increasing over the last 60 years. It is evidenced that the yield of corn increased from 2250-3000 kg/ha in 1960s to 12000-15000 kg/ha at present. The corn yield of the dam-trapped farmland is 1.5-2.0 folds of that of the terrace land. The nutrient use efficiency and water use efficiency of corn in the dam-trapped farmland are much higher than those of terrace land. It can be seen that check dam have the powerful function mitigating the losses runoff and sediment, and dam-trapped land can play the critical parts in sustaining grain production and insuring food security in the hilly and ravine region of the Loess Plateau. 

Keywords: soil erosion; check dam; dam-trapped farmland; grain production; food security; hilly and ravine region; Loess Plateau

How to cite: Wang, B., Dang, W., and Dang, T.: The Roles of Check Dams and Dam-Trapped Farmlands in the Hilly and Ravine Region of the Loess Plateau: Soil Erosion Control, Grain Production and Food Security , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6838, https://doi.org/10.5194/egusphere-egu21-6838, 2021.

EGU21-2161 | vPICO presentations | SSS2.10

Influence of Loess Plateau check dams on catchment flood hydrology across varying stages of lifespan

Shuilong Yuan, Peng Li, Peng Shi, and Zeyu Zhang

The over 100,000 check dams constructed across the Loess Plateau for soil and water conservation may have substantially changed the hydrological processes in the region, which, however, has not been understood yet. As a critical step towards revealing the lumped effect of check dams at the regional scale, this study explored the modified flood hydrology induced by check dams in Wangmaogou catchment, a representative small Loess Plateau watershed. A coupled hydrological and hydraulic modeling approach was applied to simulate the flooding process for different stages of deposition and topographic changes in the check dam reservoir. The results suggest a paradigm shift of the dam effect on flood attributes, which transits from a total interception in the early stage of the dam to peak reduction and flood detention, rather than a complete loss of flood control functions, when it approaches the maximum capacity of sedimentation. Under a given level of deposition, the reduction to a minor flood by a check dam was higher than that to a major flood. With the progression of siltation behind the check dam, the flood peak reduction rate, flood volume reduction rate, and flood lag time decreased accordingly. Although the check dam with a reservoir fully filled by sediment lost its ability of intercepting floods, it still exhibited a considerable ability to reduce the peaks of floods. The topographical changes contributed to the reduction of flood peak appreciably by reducing the flow velocity and retarding the flood propagation. Noticeably, this reduction augmented with the advancement of siltation and the topographic change, indicating the persistence of the hydrologic effect of check dams in a long run. As a result of hydrological changes, the reduction in flood flow velocity due to check dam suggests a substantial reduction in sediment transport and channel erosion during floods. In addition, a dam system containing multiple, cascading check dams exhibits much more significant effect in modifying both hydrologic and hydraulic properties of flood than individual dams. The current research provides a mechanistic understanding of the check dam effect on watershed hydrology under heavy rainstorms in small catchments, which sheds light on evaluating the upscaled effect of the large number of check dams on Loess Plateau regional hydrology and water resources.

How to cite: Yuan, S., Li, P., Shi, P., and Zhang, Z.: Influence of Loess Plateau check dams on catchment flood hydrology across varying stages of lifespan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2161, https://doi.org/10.5194/egusphere-egu21-2161, 2021.

EGU21-3664 | vPICO presentations | SSS2.10

Evaluation of the risk of the breaking of check dam based on a scorecard model.

beilei liu, peng li, zhanbin li, yuanyuan yang, shaobo long, and yangfan feng

Check dam is a line of defense in the comprehensive watershed management system, but with the extended operation time, the operational risk of check dam increases, coupled with the frequent occurrence of sudden heavy rainfall under the influence of climate change in recent years, further increasing the risk of dam break.

In this study, to address the current problem of untimely detection of potential dam break risk of check dam in China, we use the common variable screening based on WoE (Weight of Evidence) and IV (Information Value), establish a score card model based on logistic regression method, use KS curves and statistics, and AUC values for model evaluation, and analyze the 2016 From 22:00 on August 16 to 12:00 noon on August 17, 2016, a dam break was formed by a large rainstorm in Dalat Banner.

The following conclusions were obtained: The IV values of each variable, such as control area, total storage capacity, siltation area, storage volume, and maximum rainfall, were all greater than 0.1, and each variable had more than moderate predictive power as a function of the breaking of check dam, that is, each factor had an effect on the breaking of check dam.The IV values of precipitation factors are higher than those of check dam factors. The influence probability of precipitation factors on the breaking of check dam is about 67%, and the influence probability of check dam factors on the breaking of check dam is about 33%.Precipitation is a direct factor affecting the breaking of check dam, and the maximum 6-hour precipitation has the most significant effect; among the check dam factors, the control area, storage volume, and flood storage capacity have a greater effect on the breaking of check dam, accounting for more than 10%, while the siltation volume and depth have a smaller effect on the breaking of check dam, accounting for 2.85% and 2.89% respectively.Very low risk which check dam with a score of 95 or higher account for about 43%, low risk for 28%, average risk for 15%, and higher risk for 7%. Very high risk accounted for 5% and there was only one dam with danger which is rated below 10.

This study aims to monitor and warn the operation of check dam to ensure the safe operation of the check dam system and maintain the ecological security of the Loess Plateau.

How to cite: liu, B., li, P., li, Z., yang, Y., long, S., and feng, Y.: Evaluation of the risk of the breaking of check dam based on a scorecard model., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3664, https://doi.org/10.5194/egusphere-egu21-3664, 2021.

The historical landscape condition of discontinued river before discontinued flow is one of the core research fields of river ecological restoration and an important historical reference for the ecological restoration of discontinued river corridor. In this paper, the landscape condition of Yongding River, a discontinued river in northern China, is analyzed before its cut-off. Through the early KEYHOLE satellite high-definition image data interpretation analysis, the landscape type map of the river corridor before its cut-off was drawn. The overall winding degree (1.27) and the overall horizontal and vertical structure of the river before its cut-off were determined. In addition, the area proportion of the key landscape types in river corridor, such as channel, mid-channel bar and floodplain, is 12.82%, 8.8% and 16.29% respectively, and the morphological characteristics and distribution of the above key landscape types in each section of the river can be determined by quantitative analysis. On this basis, the landscape pattern index analysis method can be used to analyze and calculate the overall landscape pattern of the river corridor before cut-off. Combined with relevant historical hydrological data, the historical state of the river before its cut-off can be restored to a certain extent. These results are of great support to the channel ecological restoration, floodplain ecological reconstruction and riverbank ecological restoration.

How to cite: Xu, X.: Historical landscape condition study of discontinued river corridor based on satellite image data analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3743, https://doi.org/10.5194/egusphere-egu21-3743, 2021.

Changes in land use patterns have important implications for soil structure and soil nutrient transport processes. This paper is based on the project of returning farmland to forests in the Loess Plateau-Ziwuling area of China. Explore the phase changes of the aggregate structure and nutrients content and its effect on soil infiltration and erodibility during the changing land use process. Identify the effective time domain for soil management in the area, which provide a scientific basis for coordinating regional land use and efficient soil erosion control. The results showed that with the increase of soil recovery/opening time, the content of soil water stable aggregates (SWAG), soil organic matter (SOM), total nitrogen (TN) and total phosphorus (TP) showed an increasing /decreasing trend. In the process of soil reclamation, the content of organic matter in large-size aggregates (>5mm) decreases first at a higher rate, while in land restoration process, the content of organic matter in small-sized (2-5mm) aggregates increases rapidly. With the increase of soil reclamation time, the initial time of runoff production is advanced. In the 30-year of the land restoration process, the erodibility K decreased by 87%, and the SOC content has reached 96% to the common forest level, indicate that the soil quality is greatly improved when the land returns to this moment, the ability to resist erosion reaches a certain level and tends to be stable, and it is considered that the input and output of the governance before the time node is relatively high.

How to cite: Zhang, Y., Li, P., and Xu, G.: Response of soil nutrient structure and aggregate strength to land use in a typical area in the Loess Plateau, China , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4184, https://doi.org/10.5194/egusphere-egu21-4184, 2021.

The Loess Plateau is located in arid and semi-arid region, and the fragmentation of vegetation patches is large. However, the combination of vegetation patches to the runoff and sediment yield on the slope is not clear yet. To evaluate the influence of vegetation patch type and number on runoff, sediment and hydrodynamic parameters, this study established field runoff plots with different landscape patch types, including bare land, S-road patches, strip patches, grid patches and random patches, as well as different quantities patches of 5, 10, 15 and 20. The results showed that the runoff yields of the four vegetation patch types decreased by 16.1%–48.7% (p<0.05) compared with that of bare land, whereas sediment yields decreased by 42.1%–86.5% (p<0.05). Also, the resistance coefficients of the poorly connected patch patterns, including strip patches, grid patches and random patches, ranged between 0.2–1.17 times higher than that of the well-connected S-road patch pattern, and the stream power decreased by 33.3%–50.7% (p<0.05). Under a uniform distribution of vegetation patches, the runoff rate and sediment yield decreased significantly with an increased number of patches. Although the increase in the number of vegetation patches also resulted in a decrease inflow shear stress and stream power to different degrees, the differences between the combinations with similar patch numbers were not significant. Besides, the sensitivity of soil to erosion decreased with an increasing number of the patch in the vegetation landscape, whereas the sensitivities of patch combinations with poor connectivity were lower than those with good connectivity. From this perspective, the optimization of vegetation in the Loess Plateau region requires sufficient consideration to reducing the connectivity of vegetation patches and increasing the density of patches.

How to cite: Sun, R., Zhang, J., and Ma, L.: Landscape Patches Influencing Runoff and Sediment Yield and Flow Hydrodynamics in The Loess Plateau, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5930, https://doi.org/10.5194/egusphere-egu21-5930, 2021.

EGU21-1801 | vPICO presentations | SSS2.10

Content of heavy metals and polycyclic aromatic hydrocarbons in soils of vicinities the Bulgarian Antarctic station "St. Kliment Ohridski"

Timur Nizamutdinov, Evgeny Abakumov, Rossitsa Yaneva, and Miglena Zhiyanski

Currently, more and more researchers are recording increased pollution levels of chemicals in the environment of the Antarctic regions. It is noted that mostly concentrations are fixed for non-typical chemical contaminants of anthropogenic origin. These can be Heavy Metals (HM), Polycyclic Aromatic Hydrocarbons (PAH) or Polychlorinated Dibenzodioxins (PCDD). It is well known that these classes of substances have a negative impact on human health and are detrimental to the development of endemic species, as well as having carcinogenic and mutagenic effects.

The problem of pollution of Antarctic territories is especially relevant recently. As the scientific interest in these territories increases, the anthropogenic load on the fragile Antarctic ecosystems also increases in parallel. Chemical contaminants can enter the Antarctic continent in a variety of ways. Researchers bring large volumes of diesel fuel and other fossil fuels with them to heat research stations. This often results in oil spills and the discharge of contaminated wastewater into sub-Antarctic waters. Entry is also possible as a result of transboundary transfer of atmospheric emissions from the territories of Australia and South America, which are deposited in Antarctica.

In our investigation, 15 priority concentrations of PAHs and some heavy metals in the soils of Livingston Island (Antarctic Peninsula) were analyzed based on the analysis of soil samples obtained during the Bulgarian Antarctic Expedition. The data on PAH concentrations in soils allowed us to calculate different isomer ratios of aromatic hydrocarbons, which may indicate the nature of the origin of the contaminants.

Significant differences were recorded in the content of chemical contaminants between soils in the station area and its vicinity. Thus, for instance, the content of Naphthalene, Acenaphthene, Naphthalene and Pyrene in soils at “St. Kliment Ohridski” Station (Cryosol Toxic Transportic, WRB 2014) was at 170, 41, 38 and 60 µg/kg, respectively. While in the soils (Cryosoils Leptic Stagnic, Cryosol Leptic Ornitic Hypersceletic, Cryosol Turbic Gleyic, WRB 2014) around the station the content of similar PAHs were 53, 6, 20, and 21 µg/kg.

The highest concentration of heavy metals was also recorded in soils exposed to anthropogenic load. The concentrations of Cu, Pb, Zn, Cd, Ni and Cr were 22.6, 10.7, 75.7, 0.28, 10.1 and 5.25 µg/kg, respectively, in the soils of the Bulgarian station. For undisturbed Antarctic soils of Livingstone Island, heavy metal concentrations were significantly lower.

We also calculated some isomeric ratios of PAHs. The values of these ratios allowed us to reveal the nature of the origin of PAHs on Livingstone Island. In the samples collected at “St. Clement Ochridski” Station, the sources of PAHs are predominantly pyrogenic processes, combustion of liquid fossil fuels, and traffic source.

This work was supported by Russian Foundation for Basic Research, Projects No 18-04-00900, 19-54-18003 and 19-05-50107

How to cite: Nizamutdinov, T., Abakumov, E., Yaneva, R., and Zhiyanski, M.: Content of heavy metals and polycyclic aromatic hydrocarbons in soils of vicinities the Bulgarian Antarctic station "St. Kliment Ohridski", EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1801, https://doi.org/10.5194/egusphere-egu21-1801, 2021.

EGU21-1933 | vPICO presentations | SSS2.10

Application of Xin'anjiang Model and Wetspa Model in the Inflow Forecasting of Shiquan Reservoir

Siyu Cai, Ruifang Yuan, Weihong Liao, and Liang Wu

In order to improve the accuracy of the inflow forecasting of Shiquan Reservoir in the Han River Basin, this paper compared the application effects of Xin'anjing model and Wetspa model. The study collected the rainfall and runoff data from 2009 to 2015, as well as the DEM, land use and soil data with 1000´1000m grid size. The model calibration and verification periods were from 2009 to 2012 and from 2013 to 2015, respectively. In addition to using the runoff depth and the determination coefficient to evaluate the accuracy of the two models, the flow relative error CR1, model confidence coefficient CR2, Nash-Sutcliffe efficiency CR3, logarithmic version of Nash-Sutcliffe efficiency CR4 for low flow, improved Nash-Sutcliffe efficiency CR5 for high flow were adopted to analyze the simulation results of the two models. The results showed that the simulation results of the Wetspa model could be used as a supplement to the simulation results of the Xin'anjiang model, providing high-precision flood forecasting results for the scheduling decisions of Shiquan Reservoir in terms of time and space.

How to cite: Cai, S., Yuan, R., Liao, W., and Wu, L.: Application of Xin'anjiang Model and Wetspa Model in the Inflow Forecasting of Shiquan Reservoir, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1933, https://doi.org/10.5194/egusphere-egu21-1933, 2021.

EGU21-2147 | vPICO presentations | SSS2.10

Prediction of Surface Water Resources in Danjiangkou Basin Based on ESP and Distributed Hydrological Model

Ruifang Yuan, Siyu Cai, and Weihong Liao

 The prediction of surface water resources in the Danjiangkou Basin is of great significance for the design of the water transfer plans for the South-to-North Water Diversion Project. However, it is difficult to obtain high-precision simulations for mid- and long-term hydrological forecasting. Based on the thought of extended streamflow prediction (ESP) and distributed hydrological models, this paper proposed a set of forecasting systems for predicting the annual surface water resources in the Danjiangkou Basin. Firstly,  the Wetspa model  was established to forecast the inflow of Danjiangkou reservoir. The Nash efficiency coefficients of the monthly average runoff during the calibration period (2006-2012) and verification period (2013-2016) were 0.97 and 0.95, respectively. Secondly, it was assumed that the rainfall of 2017 could be predicted by the rainfall forecasting model, then the rainfall process was obtained based on the ESP and the runoff process of the basin outlet was calculated through the Wetspa model. Finally, the predicted surface water resources of the Danjiangkou Basin in 2017 was 45.448 billion m3, and the actual surface water resources is 40.395 billion m3, with a relative error of 12.51%. The results showed that the prediction of surface water resources in Danjiangkou Basin based on ESP and distributed hydrological model could provide a certain reference for the design of water transfer plans of the Danjiangkou Reservoir.

Key words: Water resources prediction; ESP; Wetspa model; Nash coefficient

How to cite: Yuan, R., Cai, S., and Liao, W.: Prediction of Surface Water Resources in Danjiangkou Basin Based on ESP and Distributed Hydrological Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2147, https://doi.org/10.5194/egusphere-egu21-2147, 2021.

Rock outcrops are common features of the karst ecosystem The bare rock rate is an important indicator for rocky desertification grades classification, and its accurate extraction can benefit for understanding the distribution characteristics of rock outcrops in desertification areas and the classification of rocky desertification grades. In order to explore the distribution pattern of surface bare rocks in the typical geomorphic environment of the Karst gabin basin, the Mengzi gabin basin was carried out as the research site. The combination of UAV shooting images and digital image processing technology were used, the characteristics of bare rock rate on the karst fault basin after vegetation restoration were shaped. Our results showed that digital image processing technology can be used for extraction of bare rock rate in Karst area, and the effective combination of UAV technology and digital image processing technology can quickly obtain bare rock rate data of typical landform in Karst gabin basins. After performing drone aerial photography on 26 typical landform information under different bare rock distribution conditions on the Mengzi gabin basin, the results of the image processing analysis showed that the bare rock rate is between 2.7%-28.9%. The research provide technical support for the assessment of the karst ecosystem degradation and the evaluation of the current status of rocky desertification in karst gabin basin

How to cite: Yin, Z. and Shan, Z.: Preliminary research on a method of outcrops extraction on Karst Gabin ecosystem based on digital image processing: the case of the Mengzi Gabin basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10513, https://doi.org/10.5194/egusphere-egu21-10513, 2021.