SSS2.7

EDI
Soil Erosion, Land Degradation and Conservation

Soil erosion is a major global soil degradation threat to land, freshwater and oceans. Scientific understanding of all erosional physical processes controlling soil detachment, transportation, and deposition is vital when developing methods and conservation alternatives to minimize the impacts associated with soil degradation.

This session will discuss the State-of-the-Art of the latest soil erosion measurements, monitoring and modelling techniques in agriculture, forest and rangelands. Our main objective is to scientifically discuss soil erosion but also to explore/present solutions that may help farmers and policy makers; supporting the ongoing activities aiming at achieving the SDG Target 15.3 land degradation neutral world by 2030 and the upcoming UN Decade on Ecosystem Restoration (2021-2030). This session will also discuss recent studies supporting improved understanding of gully and rill erosional physical processes, their impact locally, their off-site effects on sedimentation, and subsequent development of mitigation strategies.

Co-organized by GM4/NH8
Convener: Pasquale Borrelli | Co-conveners: Henrique Momm, Panos Panagos, Rafael Giménez, Robert Wells, Rafael Muñoz-Carpena, Diana VieiraECSECS
vPICO presentations
| Mon, 26 Apr, 11:00–12:30 (CEST), 13:30–15:00 (CEST)

vPICO presentations: Mon, 26 Apr

Chairpersons: Henrique Momm, Rafael Giménez, Robert Wells
11:00–11:02
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EGU21-391
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ECS
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.

11:02–11:04
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EGU21-1478
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.

11:04–11:06
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EGU21-2613
Wolff Charlotte, Choanji Tiggi, Derron Marc-Henri, Fei Li, and Jaboyedoff Michel

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.

11:06–11:08
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EGU21-3399
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ECS
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.

11:08–11:10
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EGU21-3601
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.

11:10–11:12
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EGU21-3676
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ECS
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.

11:12–11:14
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EGU21-3742
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ECS
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.

11:14–11:16
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EGU21-6378
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ECS
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.

11:16–11:18
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EGU21-12652
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ECS
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.

11:18–11:20
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EGU21-9591
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ECS
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.

11:20–11:22
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EGU21-13060
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ECS
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.

11:22–11:24
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EGU21-14339
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ECS
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Highlight
Lea Epple, Andreas Kaiser, Marcus Schindewolf, and Anette Eltner

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.

11:24–11:26
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EGU21-1524
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ECS
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.

11:26–11:28
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EGU21-1976
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ECS
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.

11:28–11:30
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EGU21-2272
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ECS
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Highlight
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.

11:30–11:32
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EGU21-2464
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ECS
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.

11:32–12:30
Lunch break
Chairpersons: Pasquale Borrelli, Panos Panagos, Diana Vieira
13:30–13:32
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EGU21-2538
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ECS
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.

13:32–13:34
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EGU21-2666
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ECS
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.

13:34–13:36
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EGU21-2707
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.

13:36–13:38
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EGU21-3149
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.

13:38–13:40
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EGU21-3698
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Highlight
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.

13:40–13:42
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EGU21-4036
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.

13:42–13:44
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EGU21-5008
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Highlight
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.

13:44–13:46
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EGU21-5713
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ECS
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.

13:46–13:48
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EGU21-8445
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ECS
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.

13:48–13:50
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EGU21-9182
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ECS
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.

13:50–13:52
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EGU21-9544
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ECS
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.

13:52–13:54
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EGU21-9717
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ECS
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.

13:54–13:56
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EGU21-10087
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ECS
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Highlight
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.

13:56–13:58
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EGU21-13701
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ECS
Károly Tatárvári and Attila Piros

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.

13:58–14:00
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EGU21-1432
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ECS
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.

14:00–14:02
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EGU21-14186
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ECS
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.

14:02–15:00