SSS2.3

Indian is worst affected by soil erosion, especially due to erosion induced by rainfall. A factor of Universal Soil Loss Equation (rainfall erosivity factor) needs to be estimated throughout the country to assess the soil erosion in the country. Indian climate is dominated by monsoons, and their intensity and distribution vary significantly throughout the country. Rainfall erosivity is solely derived from the rainfall intensity, which is a function of climatic properties. In this study, the distribution and variability of the rainfall erosivity factor (R factor) had been analyzed in different regions and sub-divisions of India as classified by India Meteorological Department (IMD). For estimation of rainfall erosivity, the widely adopted principle of kinetic energy and rainfall intensity had been used. A well-known precipitation index, Modified Fournier Index (MFI), was also calculated to check its influence on the R factor. Regression equations in the form of power-law are derived for all regions of the country to establish the relationship between the R factor and MFI. Further, an analysis at the sub-divisional level was also performed to visualize the spatial variability of the R-factor throughout the nation. South peninsula India with the lowest average R factor of 615.61 MJ-mm/ha/h/yr, was recognized as least vulnerable to rainfall erosivity while the East and Northeast India was recognized as most susceptible with a highest R factor of 3312.39 MJ-mm/ha/h/yr. About 36% of the entire subdivisions of the country were spotted with an average rainfall erosivity factor higher than the national average rainfall erosivity factor, and hence they are more prone to erosion induced by rainfall. Estimating rainfall erosivity factors at sub-divisional and regional levels will help policymakers and watershed experts prioritize the watershed management practices to counter soil erosion induced by rainfall erosivity.

Keywords – Rainfall erosivity, IMD, Spatial variability, Climate, Precipitation index

How to cite: Raj, R., Saharia, M., Chakma, S., and Rafieeinasab, A.: Spatial Variability of Rainfall Erosivity over India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-152, https://doi.org/10.5194/egusphere-egu22-152, 2022.

Rainfall erosivity is one of the main inputs for soil erosion modelling. Long high-resolution rainfall time series are needed for the estimation of rainfall erosivity but these are likely to be lacking at many locations around the globe. An alternative approach could be the generation of synthetic rainfall time series using stochastic rainfall models. In this study, four methods for estimating the rainfall erosivity were evaluated at ungauged sites:

i) estimation from regionalised observed 5 minute rainfall time series,

ii) direct regionalisation of the rainfall erosivity estimated from observations,

iii) estimation from 5 minute rainfall time series disaggregated from daily observations,

iv) estimation from rainfall time series generated by a regionalized stochastic rainfall model.

Data from 159 stations from Lower Saxony, Germany, were used to evaluate the performance of different methods. All tests were performed using the leave-one-out cross validation method. Additionally, we also analysed the minimum time series length necessary to adequately estimate the rainfall erosivity.

The results indicated that the direct regionalization of the mean annual rainfall erosivity yielded the best performance in terms of relative bias followed by the regionalization of the 5 minute rainfall data. However, the main advantage of the rainfall generators is that they can generate long synthetic time series and can also provide estimates of other rainfall erosivity characteristics such as number of erosive rainfall events, etc. Applying the alternating renewal model indicated that more than 60 years of data are needed to obtain a stable estimate of rainfall erosivity and that rainfall erosivity estimations using 5 years of data can lead to significant uncertainty. Moreover, it was also found that the rainfall erosivity calculations are sensitive to the resolution of the input data.  

Acknowledgment: The results of the study are part of the bilateral research project between Slovenia and Germany “Stochastic rainfall models for rainfall erosivity evaluation” (BI-DE/18-19-008). 

How to cite: Bezak, N., Pidoto, R., Müller-Thomy, H., Shehu, B., Callau-Beyer, A., Zabret, K., and Haberlandt, U.: Investigation of the applicability of rainfall generators for the estimation of the rainfall erosivity for ungauged locations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2210, https://doi.org/10.5194/egusphere-egu22-2210, 2022.

Every year 12.5 million tons of plastic are used in agricultural production across the globe with plastic films accounting for 75% of this plastic. Once added to the soil, removing agricultural plastic is challenging as exposure to sunlight and other environmental elements fragment the plastics into macro- and microscopic pieces. In addition to this direct input, agricultural soils accumulate microplastics from several other sources e.g., biosoilds input, runoff from roads and atmospheric deposition. Soils are usually thought of as sinks for plastic waste but growing literature suggests mismanaged agricultural soils could be significant sources of plastics to aquatic and other terrestrial environments. In this study, we investigated the process of microplastic movement in response to rainfall and overland flow. We compared the movement of two types of plastic (linear low-density polyethylene and acrylic) in two size fractions with sand particles in rainfall simulation experiments. We examine the extent to which plastic particles are preferentially eroded compared to fine sand particles, alongside the relative importance of particle size and polymer type for controlling the erosion of plastics from soil.

How to cite: Severe, E., Surridge, B., and Quinton, J.: Processes controlling the transportation of microplastics in agricultural soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11484, https://doi.org/10.5194/egusphere-egu22-11484, 2022.

An extensive erosion plot database measuring soil loss and runoff under natural rainfall in China was compiled to gain new understanding of the overall response of the soil loss and runoff rate to land use, slope gradient, slope length and mean annual precipitation. Our results show that land use dominates the variation of soil loss and runoff: Soil loss and runoff rates on land covered by natural vegetation are one to three orders of magnitude lower in comparison to rates on agricultural land that is strongly disturbed by anthropogenic activities. Slope gradient and slope length affect soil loss and runoff rates on cropland but there is no statistically significant effect on either soil loss or runoff rate on permanent vegetation. This implies that different extrapolating relationships need to be used for cropland in comparison to land with permanent vegetation when erosion plot data are used to assess the erosion risk over large areas. Runoff rates consistently increase with mean annual precipitation. The relationship between soil loss and mean annual precipitation is different and is nonlinear for all land use types, with a clear increase of soil loss with precipitation up to a mean annual precipitation of ca. 700 mm yr^-1, a subsequent decline and a second rise when the mean annual precipitation exceeds ca. 1400 mm yr^-1. This non-linear response can be attributed to the interplay of an increasing rainfall erosivity and an increasing protection due to vegetation cover with increasing mean annual precipitation. It also implies that the effect of climate change on the erosion risk is not straightforward but depends on how both rainfall erosivity and vegetation cover change with changing climate.

How to cite: Zhao, J.: Nonlinear response of soil erosion to mean annual precipitation: evidence from erosion plot data in China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2546, https://doi.org/10.5194/egusphere-egu22-2546, 2022.

Scale issues in runoff and sediment delivery (SIRSD) is a hot and frontier topic in the fields pertinent to hydrology and soil erosion. This study combined bibliometric analysis and data mining to provide a systematic and holistic review of global SIRSD studies. The bibliometric results indicate that SIRSD is a comprehensive and multidisciplinary issue that has been extensively investigated with a wide variety of methods by scientists from 85 countries since the 1950s. The rapid growth of publications over the last three decades reveals that the discussions on SIRSD are attracting booming attention due to its great potentials for research and practice on various contemporary issues of environment and natural resources. Especially topics about hydrological and sediment connectivity, storm flood, nonpoint pollution, landslide and debris flow are drawing increasing concerns under the context of climate change. Thematic structure analysis indicates that SIRSD field centres the spatial scaling issues in the delivery of suspended sediment, including sediment budget analysis and sediment delivery ratio (SDR) estimation. Compared to studies dealing with erosion and sediment that mainly focus on the spatial scale, studies related to hydrological runoff and climate tend to discuss more temporal scale issues. Regarding the study distribution, most studies cluster on the time scale from an event to 10 years and the spatial scale from plot to meso-watershed (10 m²-1000 km²) and tend to appear in regions that feature free-flowing rivers with rapid agricultural development. Based on the mined 1039 pairs of data on the relationship between SDR and the watershed area, we built a global view of the spatial effect on SDR. The spatial scale effect on SDR is most prominent in Europe, followed by the USA, then the Global average, while most gentle in China due to its high topographic variability. On the contrary, the average SDR is highest in China (0.51), followed by the Global case (0.37), then the USA (0.34), while lowest in Europe (0.28) due to its low mean topographic slope. From this review, we identified several research gaps: 1) lack of multi-scale studies with nested across-scale design and studies on the spatial scale effect on runoff delivery; 2) considerable gaps among the results obtained from different regions, methods, and scales; 3) debatable and unclear questions on the spatio-temporal scale of underground water and soil loss in the karst region. Moreover, we emphasize three areas for future research: 1) scale issues of flood processes regarding extreme rainstorms under climate change; 2) scale transformation methodology and multi-scale modelling of hydrology, erosion, and sediment transport and their integrations with the climate models; 3) comparative study in different regions to bridge the regional gaps.

How to cite: Ke, Q. and Zhang, K.: Scale issues in runoff and sediment delivery: a global review and statistical analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3371, https://doi.org/10.5194/egusphere-egu22-3371, 2022.

Soil erosion by water is a severe problem throughout the world that threatens soil security and the health of water bodies. This problem is aggravated by global climate change, leading to more intense rainfall and drought events. Moreover, soil erosion also intensifies the impacts of drought by reducing the soils' capacity to hold water and maintain sustainable crop yields. This project aims to evaluate the current status and future evolution of soil security in the Guadalquivir basin. For this purpose, we use a combination of predictive modelling and estimations of long-term soil erosion-deposition rates based on field observations and measurements of fallout radionuclide (FRN) tracers in representative catchments. We test and apply a novel method for analyzing ^239+240Pu isotopes, that offers a much cheaper way of analysis and hence a potential new standard to estimate long-term soil erosion-deposition rates. Spatially distributed estimations of long-term soil erosion-deposition rates are used to calibrate and evaluate the soil erosion models RUSLE and MMF-TWI which will then be used to assess present and future soil resource status in the catchments of study. Here, we present the preliminary results of this project, particularly the results obtained by the analysis of ^239+240Pu  isotopes in an olive grove catchment and how these results compare against the more established ¹³⁷Cs analysis and estimations of soil truncation based on measurements of the height of olive tree mounds.

How to cite: García-Gamero, V., Peñuela, A., Mas, J. L., Peña, A., Hurtado Bermúdez, S., and Vanwalleghem, T.: Quantifying the impact of soil erosion on soil security by using alternative fallout radionuclides, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4173, https://doi.org/10.5194/egusphere-egu22-4173, 2022.

Soil erosion is high in hillside orchards in Spain. Climate change is causing an increase in the length of dry periods and intensity of rainfall, which exacerbates soil loss from fields. Due to the lack of rain during the summer, orchard farmers, concerned about water competition for tree crops, remove ground cover. However, without raindrop interception the soils are vulnerable to erosion and gullying. While cover crops between tree crops are beneficial in controlling soil erosion, farmers are slow to take up this practice. Both a mesocosm experiment identifying the value of vegetation cover, and survey responses from farmers about erosion management practices are outlined below.

Rainfall simulation was used in a mesocosm experiment to determine the effect of plant cover on sediment loss. Three species native to Spain were used in five treatments consisting of Brachypodium distachyon, Medicago sativa, Silene vulgaris, a mix of the three species, and a bare plot. The plots were raised to a 10^o angle before subsampled runoff and sediment was collected under simulated rainfall. A questionnaire was sent to crop tree farmers in Spain asking about their experiences of soil erosion, techniques used to combat it, if any, and their views on methods of soil and water conservation.

Significantly higher (p < 0.05) rates of sediment loss were measured from the bare plots (34.26 ± 19.85 g min^-1), relative to the vegetated ones (6.13 ± 8.27 g min^-1). This indicates the importance of cover crops to reduce soil erosion. The farmers responding to the questionnaire are aware of this. From a total of 26 respondents, 88% believe that cover crops decrease erosion. However, 58% think that lack of knowledge about effective methods of erosion control is a barrier to implementing techniques.     

This presentation will give an overview of the methods used in carrying out rainfall simulation and the questionnaire, in addition to the results gathered.

How to cite: Ripley, H., Stevens, C., and Quinton, J.: Impact of plant cover on soil erosion, and barriers to cover crop use in Spanish orchards., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4953, https://doi.org/10.5194/egusphere-egu22-4953, 2022.

One of the strongest challenges for European agriculture is to simultaneously reduce its negative environmental impact and at the same time, remain competitive. A key aspect of the environmental impact is the ongoing soil degradation. Within the Soil Care project, sustainable agricultural practices were investigated that could improve soil quality, termed soil improving cropping systems (SICS); four plausible scenarios were developed with different levels of SICS uptake. In this study we aimed to evaluate how such SICS, through the different scenarios, impact crop yield, soil organic carbon content and land degradation (specifically erosion and soil water dynamics) across Europe, through the application of the PESERA and dyna-QUEFTS models. The Pan-European Soil Erosion Risk Assessment (PESERA) model simulates biophysical processes including above-ground biomass production, soil erosion risk, soil water deficit and soil humus content and was adapted and calibrated for Europe. The dyna-QUEFTS model calculates nutrient limitations and was used to calculate crop yields using PESERA output information. All four scenarios were run from current (2020) until 2050 and for two climate trajectories. Results indicate that the ‘Caring and Sharing’ scenario likely provides the best sustainability impacts (i.e. stable or increased SOC contents and reduced erosion) due to widespread uptake of SICS, compared to the ‘Race to the Bottom’ scenario, in which no SICS were taken up, although regional differences can be seen from the spatially explicit maps that the modelling produces. While, by necessity, the models are a simplification of the reality and assumptions and input data quality affect the results, a comparative analysis of the scenarios and their likely effect can still be made and will be helpful for agricultural policy development across Europe. In addition, the modelling tool provides the opportunity to further analyze which SICS are effective where and to explore the impacts of SICS implementation.

How to cite: Baartman, J., Nunes, J. P., Fleskens, L., Vanhout, R., Gai, L., and Van Delden, H.: The effects of Soil-Improving-Cropping-Systems (SICS) across Europe: a simulation study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2809, https://doi.org/10.5194/egusphere-egu22-2809, 2022.

Temporary cover crops are a well stablished erosion control tool in Mediterranean tree crops such as olives or vines. Short-term (3-4 years) studies have stablished their beneficial effect in term of reducing runoff and soil losses (e.g. Gómez et al. 2009) at hillslope scale. There are few studies which have measured their hydrologic impact in the long-term. Gómez et al. (2021) in a long-term study of runoff and soil losses at hillslope scale in an olive orchard on a vertic soil noted how the reduction of runoff losses using temporary cover crops as compared to a bare soil was less than expected.

Santa Marta is a commercial olive orchard located nearby Seville, Southern Spain, with a mean slope of 11 %, with a sandy-loam textural class, and an average annual precipitation of 534 mm. In 2003, two closed runoff plots (60 long, 480 m²) where regular machine traffic during farm operations was allowed. Four additional plots where stablished in 2005. Since then, runoff and sediment have been collected to determine soil erosion rates, with more details in Gómez et al. (2009). In two of these plots a bare soil management, CT, implemented with regular passes (1 to 3 a year) of chisel has been maintained, while in the other four plots temporary covers controlled by mowing had been used. In 2005 and 2006 two of these plots were seeded with a mix of species, CCm, to enhanced biodiversity, while the other two plots have since the start of the experiment regularly seeded with short-term cycle annual grasses.

During the period 2003-2020 the experiment received an average annual, from 269 to 859 mm, and an average rainfall erosivity of 830 MJ mm ha^-1 h^-1 yr^-1, from 268 to 1750. Average annual runoff and soil losses for the CT treatment were 57.5 mm and 22.9 t ha^-1. For the CCg treatment the average losses were 33.8 mm 2.6 t ha^-1 and for the CCm 33.7 mm 2.6 t ha^-1 without statistically significant differences, at p<0.05 using a Kruskall-Wallis test, in runoff or soil losses between the CCg and CCm treatments. There was a significantly statistical difference in runoff and soil losses between the CT and both CC treatments. The use of temporary cover crops in an olive orchard with moderate machine traffic had a huge effect in reducing erosion, cumulative soil losses were 402.2 t ha^-1 in CT vs. 39.1 t ha^-1 in CC, while moderate in runoff, 57.1 vs. 33.5 mm year^-1. We discuss the temporal evolution of these differences and its implications for soil management, linking them to some soil properties analysed during this time period within the plots.

References:

Gómez, J.A., et al. 2009. The influence of cover crops and tillage on water and sediment yield, and on nutrient, and organic matter losses in an olive orchard on a sandy loam soil. Soil and Tillage Research 106: 137-144

Gómez, J. A., Guzmán, G. 2021. Long-term evaluation of cover crops on soil and runoff losses under trafficked conditions in olive orchards. EGU21-606, https://doi.org/10.5194/egusphere-egu21-606.

How to cite: Gomez, J. A., Montoliu, J., and guzman, G.: Long-term hydrologic effect of temporary cover crops in an olive orchard on a sandy-loamy soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2252, https://doi.org/10.5194/egusphere-egu22-2252, 2022.

Soil erosion causes major problems of land degradation in agricultural systems leading to losses of soil fertility. Rubber tree is one of the main tropical perennial crops with about 13 million hectares of plantations worldwide in 2018. In the early stage of a rubber plantation, soil is especially vulnerable to degradations given the low canopy cover and heavy soil surface disturbance related to clear-cutting of the previous plantation. This study aims at assessing runoff and soil losses as well as understanding the main soil factors influencing soil erosion in a young rubber plantation in Côte d’Ivoire. We intensively measured soil runoff, soil detachment, soil structure maintenance and soil macrofauna for 2.5 years under different managements of logging residues and the use or not of a legume cover crop. The results showed that the restitution of logging residues has reduced runoff by 6 and soil losses by 14 compared to plot without logging residues, over the study period. The planting line where soil is kept bare was by far the most critical area in term of soil erosion. The restitution of logging residues significantly improved soil structure maintenance as well as soil macrofauna diversity. We found strong relationships between runoff, soil losses, soil structure and soil macrofauna diversity. These results evidence that the restitution of logging residues and the sowing of cover crop are appropriate agroecological practices in young rubber plantations. Our results suggest that keeping a cover in the planting line could be the most relevant lever to limit soil erosion in the context of the study.

How to cite: Mareschal, L., Janeau, J.-L., Legrand, M., Gay, F., Kouakou, A., Brauman, A., Manizan, A., Laclau, J.-P., and Perron, T.: Logging residues promote positive interactions between soil erosion, soil functioning and soil macrofauna diversity in young rubber plantations in Africa., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7414, https://doi.org/10.5194/egusphere-egu22-7414, 2022.

The potato is known as a particularly erosion-prone crop due to its late seed development and the unique structure of its seedbed (wide-rows). Therefore, improved tillage practices are needed in order to counteract and mitigate adverse effects of erosion.

This research evaluates the effectiveness of three mitigation measures – furrow greening, micro-dams heaped between furrows, and greened micro-dams – over a three-year study period in Lower Austria. Runoff plots were used to quantify surface runoff and collect each treatment's eroded material during precipitation events. The contents were emptied after each event, dried, weighed, and, if possible, analyzed for grain size distribution and nutrient composition. Additionally, the soil water content of the ridges and furrows and the potato yield was determined for each treatment in the 2021 field campaign to evaluate further effects of each treatment.

Results show that with a furrow greening soil erosion was reduced between 48 – 83% compared to the control treatment. By heaping micro-dams, soil erosion was reduced by 79 – 98%, and with the additional greening of micro-dams sediment yield was lowered by 94 – 99%. Micro-dams increased the water content in the furrows after a precipitation event but not in the ridges. Regarding potato yield, no significant difference was observed between treatments.

The results of this study show the potential of micro-dams to reduce on-site and off-site effects of soil erosion on sloped agricultural land. Depending on the steepness of the slope and the intensity of precipitation events, breaking of micro-dams can occur and therefore lose their mitigation effect. Through the additional greening of micro-dams, further stabilization could be reached, thus withholding precipitation events of higher intensities.

How to cite: Konzett, M., Schmaltz, E., and Strauss, P.: Mitigation of surface runoff and soil erosion in potato farming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8179, https://doi.org/10.5194/egusphere-egu22-8179, 2022.

Intensive soil degradation of agricultural lands during the past decades led local authorities in the Harod Catchment, northern Israel, to implement soil and water conservation practices. Herein, for the first time in Israel, we quantified the impact of these practices on water discharge, runoff/rainfall, and sediment yields at the catchment scale. We monitored two neighboring tributaries of the Harod River: Shkedim and Shunem. Both are dominated by intensive agriculture, are similar with respect to soils and rain patterns, but differ in terms of tillage and soil conservation practices - implemented in abundance in the Shkedim catchment. Inner-catchment processes were studied at the plot scale using a structure for motion photogrammetry, utilizing an unmanned aerial vehicle. At the catchment scale, we used airborne LIDAR to provide a better understanding of the extent to which different geomorphometric characteristics might influence flood discharge, suspended sediment concentration, and yield. We monitored the impact of temporal changes in vegetation cover with remote sensing. Intense storms occurring in early winter when the soil was bare and freshly tilled generated much runoff and sediment. During three field seasons, measured mean annual sediment yields were 820 and 2,000 t km⁻² y^-1 for Shkedim and Shunem, respectively. The benefits of soil conservation practices applied in the Shkedim catchment are manifested by lower runoff yields and peak discharges. Conservation practices together with milder topography were identified to limit flow continuity and to promote sinks, while in the Shunem, tillage parallel to contour lines induced higher hydro-geomorphic connectivity. Still, Shkedim soil loss is high due to cultivation of riparian zones, lack of maintenance of engineered structures, and a larger area of bare soil during winter due to rotational cropping. These blur the efficiency of soil conservation practices at the catchment scale.

How to cite: Egozi, R., Bekin, N., Prois, Y., and Laronne, J.: The fuzzy effect of soil conservation practices on runoff and sediment yield from agricultural lands at the catchment scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11215, https://doi.org/10.5194/egusphere-egu22-11215, 2022.

In order to study the influence of artificial terrain (terraced fields) on topographic factors, this paper, based on the basic principles of soil erosion and soil conservation, uses aerial photogrammetry to obtain high-precision DEM in Zhifanggou watershed, and extracts the slopes of terraced and non-terraced areas , Slope、Length and Slope Length factor, Topographic Wetness Index, Connectivity Index and Relative Path Impact Index, and analyze the changes of these factors to understand the impact of terraces on eroded terrain. The research shows that: (1) The construction of terraces makes the slope slow down, the slope length is cut off, and the LS factor becomes smaller; (2) The construction of terraced fields reduces the connectivity at the field surface and increases the connectivity at the ridge; the IC value of terraced fields is greatly affected by slope, and the IC value of non-terraced fields is greatly affected by slope length. (3) With the increase of slope, the connectivity of sediment increases and soil erosion intensifies; runoff accumulation is likely to occur in local depressions, resulting in increased connectivity of sediment. (4) The relative path impact index is effective for identifying erosion risk areas susceptible to changes in water flow paths. This paper expounds the influence of terraced fields on eroded topographic indicators and hydrogeomorphology, which is of great significance for accurately assessing the impact of terraced fields on soil erosion and for soil erosion control in the Loess Plateau.

How to cite: Qiao, B., Yang, Q., Wang, C., Pang, G., and Li, E.: Influence of terraced fields on eroded terrain indicators：take the second of gullied rolling area on the Loss Plateau as an instance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3704, https://doi.org/10.5194/egusphere-egu22-3704, 2022.

 Soil erosion is a serious environmental problem, water erosion and wind erosion pose a greater threat to the sustainable development of Pakistan. In order to provide a scientific basis for the Pakistan’s soil and water conservation, this study used sub-meter resolution sampling survey (totally 475 units) and regional soil erosion factors (R, K, LS, B) as data sources, and calculates soil erosion rate maps (5m resolution) for each sampling unit based on the CSLE model, then uses a machine learning method to quantitatively make a soil erosion rate map in Pakistan that are closer to the real soil erosion characters. Based on climate, soil, topography, vegetation and other datas, the RWEQ model was used to quantitatively estimate the soil wind erosion rate map of Pakistan. Finally, the soil water erosion and wind erosion rate maps of Pakistan were spatially overlaid, taking into account the natural conditions of Pakistan, and according to the soil loss tolerance threshold, the study area is divided into wind erosion area, water erosion area, wind/water erosion interlaced areas. The results showed that : (1) Soil erosion in Pakistan is mainly concentrated in Potohar and its surrounding areas, the desert in the southwest, and the Thar desert in southeast. (2) The Kharan Desert in Balochistan and the Thar Desert in the southeast are dominated by wind erosion, Punjab and Sindh are dominated by water erosion, and wind and water erosion are combined in the northern mountainous areas and around the Suleiman Mountains Range. This study quantitatively estimated the rate of soil water erosion and wind erosion simultaneously in Pakistan, the results can more accurately express the spatial distribution characteristics of soil erosion in the country, provide a scientific basis for policy-making of soil and water conservation.

How to cite: Yang, X., Yang, Q., Zhu, H., and Wang, L.: Quantitative Assessment and Mapping of soil water and wind erosion in Pakistan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1683, https://doi.org/10.5194/egusphere-egu22-1683, 2022.

LANDSLIDES are one of the destructive geological processes that occur throughout the world. At global scale, the landslides are one of the major natural disaster which deteriorate the soil quality at a very large scale. In the Indian Himalayan Region (IHR), the Garhwal Himalayas of Uttarakhand landslides occurred very frequently in rainy season due to the presence of fragile rocks, active tectonic activity and unplanned anthropogenic activities. Landslides causes the loss of soil nutrients and vegetation which in turn deteriorate the soil quality. They can have an enormous effect on biodiversity and significantly alter the soil quality. The rate of soil development in essential for determining the recovering capacity of soil after the losses occurred due to landslides and erosion.

Therefore, the present study analyzed the natural recovery of soil quality in terms of soil characteristics with the passage of time (chronosequence) in 4 disturbed sites of different ages i.e., 6-year-old (L1 site), 16-year-old (L2 site), 21-year-old (L3 site) and 26-year-old (L4 site) including control (undisturbed) site in the Garhwal Himalayas of Uttarakhand. 76 soil samples were collected from all the selected sites at two depths i.e., 0-15cm and 15-30cm. The collected soil samples were analyzed for various physical (bulk density (BD), particle density (PD), total porosity (TP), moisture content (MC) and sand, silt and clay content) and chemical characteristics (pH, electrical conductivity (EC), soil organic carbon (SOC), soil organic matter (SOM), mineralisable nitrogen (MN), available phosphorus (AP) and available potassium (AK). Principal Component Analysis (PCA) was done with all the 14 variables which are significantly different in order to establish minimum data set (MDS). The MDS includes SOC, AP and clay content on the basis of the PCA results. The soil quality index (SQI) was calculated using Integrated Quality Index (IQI) equation. Landslide affected sites L1, L2, L3 and L4 and control site had mean SQI scores of 0.136, 0.279, 0.447, 0.604 and 0.882, respectively.

The results have demonstrated that the control site had much better soil quality in comparison to the landslide affected sites because of its better nutrients content and better physical characteristics. The results have also shown that the soil quality tends to increase with the age of landslide, but the soil quality has not reached to the pre-disturbance level in a period of 26 years. The SQI shows the variations in landslide affected sites which could be used to detect variations in soils of disturbed areas. The results will also provide crucial information for evaluating the consequences, designing, and implementing restoration strategies.

How to cite: goyal, D. and Joshi, V.: Soil quality assessment in a chronosequence of landslides in Garhwal Himalayas, Uttarakhand, India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-494, https://doi.org/10.5194/egusphere-egu22-494, 2022.

Soil erosion represents a serious challenge for agricultural production and for the environment. Soil erosion impacts, such as reduction of fertile soil, alteration of the carbon cycle and pollution and eutrophication of water bodies, represent a significant management concern. Modelling approaches can deliver indicators on the state of soil erosion impacts and its trends, and scenarios in relation to climate and land use change. This can help define efficient and targeted mitigation strategies. However, to define such strategies, there remains a lack of modelling approaches able to provide with long term baseline information which to measure the success of the mitigation strategies as well as model evaluation approaches robust enough so model results can be trusted by users, including researchers and land managers. The MMF-TWI soil erosion model has demonstrated its ability to simulate soil erosion and the effect of agricultural management practices over centennial scales in humid environments. However, it needs to be revised and evaluated before the model can be applied more widely in other climate areas. In this study, we present a revised version of MMF-TWI incorporating infiltration excess overland flow and a robust and innovative multi-proxy model evaluation approach in an olive orchard catchment in South Spain. The evaluation approach consists of a) the comparison of model simulations with estimations of past soil loss rates obtained from both Pu fallout radionuclide tracers and tree mound measurements and b) the evaluation of the plausibility of the model behaviour by means of global sensitivity analysis.

How to cite: Peñuela, A., Garcia Gamero, V., and Vanwalleghem, T.: A robust evaluation a revised version of the MMF-TWI soil erosion model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3671, https://doi.org/10.5194/egusphere-egu22-3671, 2022.

One of the major issues of the grazing land ecosystem is high sediment yield linked to extensive land clearing and conversion of native vegetation into grazing. It is essential to model hillslope sedimentation for improved prediction of sediment yield in grazed catchments. This study evaluated the performance of Revised Universal Soil Loss Equation (RUSLE) and Modified Universal Soil Loss Equation (MUSLE) models in predicting sediment yield from grazed catchments and analyzed the effects of runoff, peak runoff rate and the RUSLE/MUSLE factor on annual sediment yield. Springvale, Brigalow, and Weany Creek catchments from Fitzroy and Burdekin Basins in Queensland, Australia, were selected as study areas. The MUSLE models performed better as compared to the RUSLE model for all three catchments. Compared to the RUSLE model, the MUSLE1 model with factors runoff and peak runoff rate was able to predict sediment yield for Weany creek and Brigalow catchment and the MUSLE2 with factors rainfall-runoff erosivity (EI₃₀), runoff, and peak runoff rate performed well for Springvale and Brigalow catchment. The study found rainfall and runoff factors in Springvale and Brigalow catchments, and runoff factor and peak runoff rate in Weany catchments contributed to the variation of sediment yield. The estimated soil erodibility factor (K) was found 14%, 24%, and 60% higher for Springvale, Brigalow, and Weany Creek catchments, respectively, compared to K-factor from the Australian Soil Resource Information System (ASRIS). This study recommends using the MUSLE model to improve hillslope sediment yield prediction in grazing lands in Central Queensland.

How to cite: Tiwari, J., Yu, B., Silburn, D. M., Bartley, R., Thornton, C. M., Owens, J., and Brooks, A.: Comparison of the Revised and Modified USLE models for prediction of sediment yield from grazing land in Central Queensland, Australia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-876, https://doi.org/10.5194/egusphere-egu22-876, 2022.

    As one of the important indicators reflecting the regional ecological environment, fractional vegetation coverage is significant for regional eco-environmental protection and sustainable utilization of resources. To understand changes in the ecological environment of the ecologically fragile areas in the Loess Plateau affected by “Grain for Green” Program and its main driving forces in the past two decades, this study taking Yulin City as a typical example of the fragile ecological environment on the Loess Plateau, to analyze spatial-temporal variations of the vegetation coverage in Yulin City during the past two decades based on the pixel dichotomy model with vegetation index, using univariate linear regression methods. The dominant factors and interaction between factors influencing the interannual changes and spatial distribution of vegetation coverage are analyzed using the partial correlation analysis and geographic detector methods during the different period in “Grain for Green” Program. Results showed that: (1) The vegetation coverage in Yulin City significantly increased (S = 0.011, p < 0.01) from 2001 to 2020. The vegetation coverage during the construction periods (2001-2010) increased significantly (S = 0.013, p <0.01); while its increase in the consolidation periods (2011-2020) was relatively slow (S = 0.005, p > 0.05). (2)The spatial distribution of vegetation coverage in Yulin City decreased from east to west from 2001 to 2020. The vegetation coverage of all counties (districts) in Yulin City shows an overall increasing trend, among which the eastern part of Yulin City has a more significant growth trend. However, the proportion of area in the construction periods (82.1%) was larger than that in the consolidation periods (58.0%). (3) The cumulative area of the Grain for Green Program was the dominant factor in the construction periods, while it was rainfall in the consolidation period. (4) Soil texture, rainfall, and land use type mainly affected the spatial distribution of vegetation coverage from 2001 to 2020. Soil texture was closely related to changes in the vegetation coverage both in the construction and consolidation periods. The spatial heterogeneity of vegetation distribution and the interaction between the main influencing factors provides a scientific basis for the precise implementation of ecological restoration measures.

How to cite: Liu, Y., Liu, B., and Zhang, J.: Spatial-Temporal Changes Of Vegetation Coverage In Yulin City And Its Influencing Factors During The Past Two Decades Since The Implementation Of The“Grain For Green” Program, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2091, https://doi.org/10.5194/egusphere-egu22-2091, 2022.

Gully erosion is an important process of land degradation that threatens soil and water resources worldwide. However, our ability to simulate and predict this process is still very limited, especially on the continental scale. Nevertheless, such models are essential for the development of appropriate land management strategies, but also to better quantify the role of gully erosion in sediment budgets. One of the main challenges is that patterns of gully erosion depend on regional patterns of controlling factors (e.g., rainfall, lithology, soils), but are also strongly determined by local factors (e.g., topography, vegetation cover, land management). This greatly increases the complexity of potential models and their data requirements. We seek to bridge this gap by developing a robust empirical model capable of predicting gully erosion at high resolution on the scale of Africa with feasible data requirements.

More precisely, we are developing a logistic probability model at 30m resolution for the entire African continent that predicts the likelihood of gully head occurrence by using GIS and spatial data sources that are available on the continental scale.  Although empirical in nature, the factors included in this model are consistent with the current process understanding of gully erosion. To calibrate and validate this model, we make use of an extensive database of 44 000 gully heads mapped over 1680 sites, 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.

Our first analyses show that gully occurrences mainly depend on topography (slope and to some extent contributing area), soil characteristics (i.e., mainly silt fraction) and vegetation cover. Combined, these factors already allow for robust and fairly reliable predictions of gully head occurrences (with AUCs of the logistic regression model around 0.7). Better incorporating the role of rainfall and climate will likely result in better predictions which is ongoing work.

Based on these results we present a first gully probability map for Africa at 30m resolution. Besides providing essential information on gully density hotspots, this offers great potential to couple our gully density model to a gully retreat rate model and to make a first assessment of gully erosion rates at the continental scale of Africa.

How to cite: De Geeter, S., Vanmaercke, M., Verstraeten, G., Poesen, J., and Campforts, B.: First gully probability map for Africa at 30m resolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4017, https://doi.org/10.5194/egusphere-egu22-4017, 2022.

Erosion caused by extreme climate conditions and intense agricultural use is a severe threat to the soil quality of dry steppe ecosystems. The susceptibility of soil to erosion depends mainly on the stability of its structure against mechanical stress, which is directly related to the stability of aggregates. However, there is no generally accepted method to determine soil aggregate stability and most tests cannot be adequately linked to disruptive forces soils experience under field conditions. Thus, our main objective was to explore the aggregate stability of steppe soils against disruptive stresses by wind and water to assess their potential erodibility. We examined 132 topsoil samples from northern Kazakhstan under two land-use types (grassland and cropland), covering a large range of physico-chemical soil properties (texture, organic carbon, inorganic carbon, pH, and electrical conductivity). We combined several methods that capture the soil`s susceptibility against mechanical stresses common in the dry continental climate: An adjusted drop-shatter technique (energy input of 60 Joule) was used to estimate the stability of dry soil against weak mechanical forces, such as wind stroking over bare soil after tillage and before crop emergence. In addition, three wet-aggregate stability tests (fast wetting, slow wetting, and wet mechanical breakdown) were used to estimate the stability of soil aggregates under various stresses caused by precipitation. Results indicate that aggregate stability was generally higher for grassland than cropland soils. Aggregate stability under both land-use types decreased along with increasing sand and decreasing organic carbon contents. The drop-shatter method suggested that only 5% of cropland soils were at high risk of wind erosion (i.e., erodible fraction <60%). In contrast, the fast wetting test revealed that  98% of the samples are unstable after a heavy rain event or snowmelt. Even after a light rain event or the raindrop impact, 54-58% of the samples were unstable and prone to erosion.

We conclude that cropland in the dry steppe of Kazakhstan is much more vulnerable to the disruptive forces caused by water than by wind. Especially the severe breakdown of aggregates during heavy rain events or snowmelts goes well in line with the increasing erosion risk under current and future climate scenarios.

How to cite: Koza, M., Pöhlitz, J., Prays, A., Mikutta, R., Kaiser, K., Conrad, C., Vogel, C., Akshalov, K., Bondarovich, A., and Schmidt, G.: Aggregate stability and potential erodibility of dry steppe soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2803, https://doi.org/10.5194/egusphere-egu22-2803, 2022.

Brazil is seen as a potential world breadbasket in which an increase of around 40% in its current production is expected by the year 2050 to attend food demand imposed by world population growth. The disorderly intensification of agriculture results in erosion, losses and exhaustion of soil nutrients, abandonment of the area, and opening of new agricultural ones. The authors were motivated by the questioning of how significant the changes at surface runoff and soil loss over time are. Thus, this work aimed to investigate the temporal component (10 years) in the surface runoff and soil loss of a typical soil found in the Cerrado biome (Brazilian Savanah), an area that shelters a large part of the national agricultural production. The study area is located in Itirapina municipality, central region of the State of São Paulo, Brazil (22º10'S, 47º52'W, elevation of 790m). The region's mean annual rainfall is about 1486 mm and humid subtropical climate, with hot summers and dry winters. The soil type found is the Orthic Quartzarenic Neosol (RQo), which occupies approximately 15% of the Cerrado biome superficial area. Surface runoff and sediment yield are monitored in rectangular experimental plots (5 meters wide, 20 meters long, and 9% slope). Monitoring takes place in six plots kept under bare soil (three plots constructed in 2011, called P1, and another three plots constructed in 2020, called P2). Runoff flows downhill and is automatically registered through large tipping buckets and then stored in large boxes (360 liters). Runoff samples are collected after each precipitation event to identify the amount of sediment in the liquid sample. To study the pedological characteristics, soil samples were collected at different depths (15, 30, 60, and 90 centimeters) of the experimental plots in 2013 and 2022 and sent to laboratory analyses such as granulometric, porosity, density, and hydraulic conductivity. It was observed that P1 has a runoff volume 10.3% greater than P2 under the same dimensions and slope. Runoff usually starts first and lasts longer at P1 than P2. P1 soil exposure to precipitation and solar radiation over 10 years modified the superficial pedological characteristics, causing: clogging of the pores, loss of superficial soil layer, particle breakdown, and deposition near the outlet plot. Currently, the sediment carried at P1 is rich in soil particles of larger dimensions while P2 has high clay contents. The differences in the hydrological responses of the experimental plots were confirmed through laboratory analyses demonstrating that P1 has lower clay, organic matter, and porosity contents in the plot surface layers compared to P2. Most runoff and soil loss monitoring are limited to campaigns covering isolated events up to 1 year, but records over a long time as given above are scarce, especially in tropical and subtropical areas, demonstrating its relevance to the soil research community.

How to cite: Schwamback, D., Sone, J., Gesualdo, G., Watanabe, A., Zepon, F., Scutti, L., Castro, L., and Wendland, E.: How do runoff and soil loss vary over time in subtropical areas?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13197, https://doi.org/10.5194/egusphere-egu22-13197, 2022.

Gullying is a common soil erosion process in Southern Ethiopia, damaging agricultural landscapes and contributing sediments to water bodies. River catchments extending across the rift escarpment within lakes Abaya and Chamo Basin in the Southern Main Ethiopian Rift are areas experiencing such problems. Impact of gullying depends on the state of activity of gullies, i.e. inactive gullies might have had a role in the landscape formation, but they can now be considered stable and not contributing to sediment delivery to the downstream, unlike the active gullies. In order to reduce the impact of active gullies, understanding the conditions under which gullies initiate, expand and stabilize is vital. In this paper, the location where new gullies initiate and where they stabilize is modelled spatially. To determine factors controlling for the initiation of new gullies, the potential gully initiation points were extracted along more than 4520 active gullies using slope and drainage area thresholds. The susceptibility of gully initiation is then modelled using logistic regression and frequency ratio methods, with a set of 14 predisposing factors. The conditions for gully stabilization are assessed by modeling the location of the head of more than 1080 inactive gullies. Highly susceptible areas for gully initiation are mainly modelled in rejuvenated landscapes downslope of knickpoints, where steep slopes have been recently formed by knickpoint propagation.most susceptible areas for gully initiation are observed in concave slopes with high topographic wetness index, whereas heads of inactive gully stabilized when slopes become convex with a lower topographic wetness index. The area under receiver characteristics curve (AUC) of the validation data ranges from 0.75 to 0.85 for all susceptibility models; prediction rate of gully initiation and stabilization vary from 70 to 93%. Our results indicate that the applied models are reliable and have very good prediction performance of gully initiation and stabilization and that such approach contrasting the gully initiation point and the gully head location enable to better understand the gullying process. The resulting susceptibility maps are a step towards contributing to the decision-making process on the optimized locations of soil and water conservation measures, and thus contributing to landscape sustainability.

How to cite: Belayneh, L., Dewitte, O., Gulie, G., Poesen, J., Stal, C., and Kervyn, M.: Modelling the spatial variation in susceptibility to gully initiation and stabilization in the Southern Main Ethiopian Rift Valley, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5566, https://doi.org/10.5194/egusphere-egu22-5566, 2022.

Intense gully erosion has sculptured remarkable channels into the Moldavian Plateau of eastern Romania. These permanent gully types are: (1) discontinuous gullies, mostly located on hillslopes and (2) large continuous gullies in valley bottoms.

This study seeks to improve our understanding of the development of 1) continuous gullies over six decades (1961-2020) and 2) discontinuous gullies over variable time-scales (mostly 17-30 years, but also including data collected since 1961) by providing quantitative information on gully evolution and processes. Several methods were used to measure and estimate gully growth. These include intensive field monitoring using the ‘stakes grid method,’ repeated levelling until 2019, analysis of aerial photographs and Caesium-137 analysis.

            As regards the continuous gullies, results indicate that gully erosion rates have significantly decreased since 1981. The mean linear gully head retreat rate (LGHR) of 7.7 m yr^-1 over 60 years was accompanied by a mean areal gully growth rate in plan (AGG) of 213 m² yr-¹.  However, erosion rates between 1961-1980 were 4.0 times larger for LGHR and 5.9 times more for AGG compared to those for 1981-2020. Two regression models indicate that annual precipitation (P) is the primary controlling factor, explaining 57% of the LGHR and 53% of the AGG rate. The contributing area (CA) follows, with ~33%. Only 43% of total change in LGHR and 46% of total change in AGG results from rainfall-induced runoff during the warm season. Accordingly, the cold season (with associated freeze-thaw processes and snowmelt runoff) has more impact on gully development. The runoff pattern, when flow enters the trunk gully head, is largely controlled by the upper approaching discontinuous gully.

The discontinuous gullies occur as single, successive chains or clusters. These are associated with small catchments (usually <100 ha in area) and ephemeral peak runoff discharges are usually ≤2 m³ s^-1. The mean LGHR for 31 gullies was 0.97 m yr^-1, indicative of a relatively small erosion rate. However, their ‘pulsatory’ development was mostly controlled by runoff accommodation when runoff enters and is conveyed through a gully. We further analysed the changing runoff pattern or ‘variable-geometry flow.’ The R² of the relation between LGHR or AGG and  (CA) indicated a weak correlation for discontinuous gullies.

How to cite: Niacsu, L., Ionita, I., Poesen, J., and Fullen, M.: Development of continuous and discontinuous gullies in the Moldavian Plateau of Romania, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10460, https://doi.org/10.5194/egusphere-egu22-10460, 2022.

Abstract:Gully erosion is one of the soil erosion types with the largest sediment yield on the Loess Plateau, and also an important part of soil erosion control on the Loess Plateau. Based on the UAV aerial photography as in 2020, with systematic sampling method in Chabagou watershed and select 32 small watershed as the basic research unit, artificial visual interpretation method is used to draw small watershed, gully ditch, gully and ancient valleys line, gully region of northern Shaanxi loess cutting groove distribution characteristics and influencing factors of medium watershed scale of research and analysis. The results showed that : (1) The intensity of gully erosion in chabagou Basin is middle reaches & GT; Downstream & gt; In the upper reaches of the basin, the length, number and area of ditches per unit area are 9.03 km, 339.04 and 7.29hm², respectively. More than 50% of the ditches are between 10m and 30m in length, and 60% of the ditches are less than 150m²; (2) The ancient gully length density, gully length density, gully strip density and gully area density were the highest in the middle reaches of the basin. (3) The positive and negative terrain area ratio and slope directly affect the gully density, showing a moderate correlation; NDVI and the proportion of cultivated land had an indirect effect on the gully density, and the correlation was strong. The length, density and number of ditches in shady slope were significantly higher than those in sunny slope. This paper can explain the development characteristics of gully at medium watershed scale in loess gully region, clarify its distribution law, and provide theoretical basis for gully erosion control. 

How to cite: zhang, C., wang, C., yang, Q., pang, G., yang, L., wang, L., and long, Y.: Study on distribution characteristics of loess gully at medium watershed scale based on UAV images, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1289, https://doi.org/10.5194/egusphere-egu22-1289, 2022.