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SSS2.8

The latest reference document of the United Nations (UN) on the status of global soil resources (FAO & ITPS, The Status of the World’s Soil Resources 2015) stresses that "…the majority of the world’s soil resources are in only fair, poor or very poor condition" and soil erosion is a major threat to soil worldwide. Soil erosion is the detachment and transport of soil particles or aggregates by action of wind, water, and gravity and is responsible for land degradation processes that end in Desertification. High erosion rates results in non-sustainable agriculture production and the need to find expensive solutions via costly governmental policies.

This session will show the State-of-the-Art of the soil erosion processes in agriculture, forest and urban areas. Our main objective is to assess the process but also to find solutions that may help farmers, policy makers and to support the ongoing research activities of the Food and Agriculture Organization of the United Nations (FAO) and the Global Soil Partnership (GSP) on soil national erosion, i.e., the new bottom-up UN Global Soil Erosion Map (GSERmap).

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Convener: Pasquale Borrelli | Co-conveners: Enric Terol Esparza, Panos Panagos, Antonio Giménez-Morera, Artemi Cerdà
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| Attendance Mon, 04 May, 08:30–10:15 (CEST)

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Chat time: Monday, 4 May 2020, 08:30–10:15

D2172 |
EGU2020-18653
Yulia Kuznetsova, Vladimir Belyaev, Sergey Kharchenko, and Anna Semochkina

Gullies are traditionally considered as one of the most active landforms in agricultural areas. In many places gully erosion leads to massive loss of fertile soil, decline of areas available for cultivation and a number of other land use complications. In addition, gullies in many cases act as the most effective runoff and sediment routing pathways, promoting better connectivity and increasing sediment delivery from cultivated hillslopes into fluvial network. Hence, gully network development may also cause significant detrimental off-site effects, including small river degradation, reservoir siltation, particle-bound pollutants concentration, etc. On the other hand, this process is often not progressive and unidirectional, but rather includes cycles of incision and head retreat alternating with infill periods. Understanding this dynamics and knowing its control factors may help to predict the future process trends for different climate and land use change scenarios, save fragile soil and water resources and design sustainable agricultural activity in changing environment.

We analyzed five different small river basins in Central European Russia to investigate the cycles of gully growth and infill. The main approach was to acquire gully network structure from topographic maps or by manual visual interpretation of satellite images. A set of topographic maps was used to map the spatial structure of gullies over the case study areas for several time intervals from mid XIX century to the end of XX century. In addition, recent satellite images were used to investigate the up-to-date (2018-2019) gully network structure and distinguish its possible latest changes related to climate or land use changes.

It is common to consider agriculture as the main factor of gully erosion activation in this area. We found that land use changes over the last 150 years lead not only to erosion rates shifts, but to incision and infill cycles. Besides, morphometric parameters of individual gullies, spatial patterns of gully network and gully density within different catchments strongly depend on local topography. Particularly important controls are topographic ranges, long profile and planform shapes of catchment slopes. Recent studies also showed that planform structure of upper parts of gully network (especially small tributary gullies of larger gully systems), as well as smooth slope depressions and periodically formed ephemeral gullies on cultivated hillslopes are in many cases strongly related to relic cryogenic features (RCF) of the Late Pleistocene cold stages. Evidence of partly infilled gullies incised into the RCFs such as ice or ice-ground wedge pseudomorphs are widely observed both on satellite and airborne images and in natural (undercut gully or small valley banks) or anthropogenic (quarries) exposures.

Interaction of climatic impact, intrinsic gully headcut retreat threshold and recent land use changes determine modern gully network conditions. The main presently observed tendency is stabilization or gradual infill of most of the small- and medium-sized gullies by sediments transported by sheet wash, rill and ephemeral gully erosion from arable fields. At the same time, small discontinuous bottom gullies are developed in larger gully systems.

This study is supported by the Russian Foundation for Basic Research (Project No. 18-05-01118a).

How to cite: Kuznetsova, Y., Belyaev, V., Kharchenko, S., and Semochkina, A.: Cycles of gully incision and infill in agricultural landscapes of Central European Russia: natural and anthropogenic factors, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18653, https://doi.org/10.5194/egusphere-egu2020-18653, 2020.

D2173 |
EGU2020-12909
| Highlight
Dongjun Lee, Jae E Yang, Kyoung Jae Lim, Jonggun Kim, and Won Seok Jang

This study is to develop the Web GIS-based surface soil erosion prediction system that informs soil information such as daily potential soil erosion, soil quality, and best management practices (BMPs). The system involves three functions that are: 1) to predict daily potential soil erosion in the study areas (e.g., Jaun-Cheon, Bukhan-Gang, Namhan-Gang, and Gyoungan-Cheon); 2) to provide the current levels of soil qualities at field scale; 3) to recommend BMPs which can improve soil qualities. This study developed a module based on MUSLE and assessed the availability of the module comparing with the measured data at sample fields (3%, 9% slope). After verification of the module, the Web GIS-based system was developed using a user-friendly interface. The users can obtain the visualized soil erosion information through the interface and compare the amount of soil erosion using the single field or multi-fields analysis tool developed in this study. Moreover, the users can find the current level of soil qualities at fields they selected and gain various applicable BMPs information. The system enables to inform non-experts to soil information without using a complex model and equation. Therefore, the system can play a significant role in recognizing the importance of soil resources and enacting laws relative to soil conservation.

How to cite: Lee, D., Yang, J. E., Lim, K. J., Kim, J., and Jang, W. S.: Development of Web GIS based Surface Soil Erosion Prediction System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12909, https://doi.org/10.5194/egusphere-egu2020-12909, 2020.

D2174 |
EGU2020-21695
Elmar Schmaltz, Georg Dersch, Christine Weinberger, Carmen Krammer, and Peter Strauss

Empirical models, such as the Revised Universal Soil Loss Equation (RUSLE) are in use since the 1950s to estimate the mean annual soil loss for single agricultural fields or spatially-distributed for larger areas (municipalities, regions or states). A particular focus on the computation of the RUSLE lies in the calculation of the respective factors on which the equation is built on and represent the erosivity of rainfall events, the erodibility of soils, the topography and land management. However, the RUSLE is highly susceptible to large errors in the prediction of the erosion rates of single agricultural parcels, due to the high variability of these factors in large areas (e.g. on national scale).

In this study, we present a parcel-sharp erosion map for the entire territory of Austria. We discuss frequent error sources of the factor computations and their consequences for the representativeness of erosion maps at nation-scale. Based on our results we discuss furthermore regional erosion hotspots and evaluate nationally funded management practices for soil erosion reduction as they are defined in the Austrian programme for an environmentally responsible agriculture (ÖPUL).

Since our approach depicts a novelty for Austria, we further describe opportunities for analysis of our results and highlight potential sources of errors, as well as regional and legal discrepancies of the distribution of national funds for soil conservation.

How to cite: Schmaltz, E., Dersch, G., Weinberger, C., Krammer, C., and Strauss, P.: Soil erosion in Austria – National calculations using regional data delivering local results for the ÖPUL programme, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21695, https://doi.org/10.5194/egusphere-egu2020-21695, 2020.

D2175 |
EGU2020-8158
| Highlight
Joris de Vente and Joris Eekhout

Climate models project increased extreme precipitation for the coming decades, which may lead to higher soil erosion in many locations worldwide. The impact of climate change on soil erosion is most often assessed by applying a soil erosion model forced by bias-corrected climate model output. A literature review among more than 100 papers showed that many studies use different soil erosion models, bias-correction methods and climate model ensembles. In this study, we assessed how these differences affect the outcome of climate change impact assessments on soil erosion. The study was performed in two contrasting Mediterranean catchments (SE Spain), where climate change is projected to lead to a decrease in annual precipitation sum and an increase in extreme precipitation, based on the RCP8.5 emission scenario. First, we assessed the impact of soil erosion model selection using the three most widely used model concepts, i.e. a model forced by precipitation (RUSLE), a model forced by runoff (MUSLE), and a model forced by precipitation and runoff (MMF). Depending on the model, soil erosion in the study area is projected to decrease (RUSLE) or increase (MUSLE and MMF). The differences between the model projections are inherently a result of their model conceptualization, such as a decrease of soil loss due to decreased annual precipitation sum (RUSLE) and an increase of soil loss due to increased extreme precipitation and, consequently, increased runoff (MUSLE). An intermediate result is obtained with MMF, where a projected decrease in detachment by raindrop impact is counteracted by a projected increase in detachment by runoff. Second, we evaluated the implications of three bias‐correction methods, i.e. delta change, quantile mapping and scaled distribution mapping. Scaled distribution mapping best reproduces the raw climate change signal, in particular for extreme precipitation. Depending on the bias‐correction method, soil erosion is projected to decrease (delta change) or increase (quantile mapping and scaled distribution mapping). Finally, we assessed the effect of climate model ensembles on soil erosion projections. We showed that individual climate models may project opposite changes with respect to the ensemble average, hence, climate model ensembles are essential in soil erosion impact assessments to account for climate model uncertainty. We conclude that in climate change impact assessments it is important to select a soil erosion model that is forced by both precipitation and runoff, which under climate change may have a contrasting effect on soil erosion. Furthermore, the impact of climate change on soil erosion can only accurately be assessed with a bias‐correction method that best reproduces the projected climate change signal, in combination with a representative ensemble of climate models.

How to cite: de Vente, J. and Eekhout, J.: The implications of soil erosion model conceptualization, bias-correction methods and climate model ensembles on soil erosion projections under climate change, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8158, https://doi.org/10.5194/egusphere-egu2020-8158, 2020.

D2176 |
EGU2020-1432
José Carlos de Araújo, Antonio Álisson Simplício, Francisco Jairo Pereira, and Carlos Alexandre Gomes Costa

The Gilbués Desertification Site (GDS) is an 8,000-km² area located in the Northeast of Brazil. It comprises large continuous areas with deep (up to 30 m), wide (up to 50 m), and long (up to 6 km) gullies, as well as severe inter-rill erosion. Inside the GDS there is an experimental site, in which almost 100 check dams were constructed a decade ago to assess their feasibility as a soil-restoration initiative. For two years (2018 and 2019) we have monitored a 15-ha watershed that contains 52 check dams so as to estimate the main erosion-related parameters as well as to assess the effectiveness of the check dams. The monitoring program consisted of (i) a climate station; (ii) four hillslopes with pins every m², measured monthly to quantify gross erosion; (iii) five flights with an accurate unmanned aerial vehicle (UAV) to identify the siltation of the check dams and to parameterize the rainfall-runoff behavior; (iv) 92 soil samples in the hillslopes and inside the check dams; and (v) four infiltration experiments. The results show that (i) the gross erosion is 8 mm.yr-1, or 10² Mg.ha-1.yr-1, a value ten times higher than the region average; (ii) based on the silting of the check dams, the sediment yield averaged 85 Mg.ha-1.yr-1, 20 times higher than the regional mean value, which is partially explained by the small size of the watersheds (10²-10³ m²); (iii) the Wischmeier vegetation C factor is 0.9, showing high degree of vegetative-cover degradation; and (iv) the sediment delivery ratio was 0.8, which could be satisfactorily represented by the Maner equation. These results show that, although the GDS corresponds to only 10% of the Boa Esperança (5,000 hm³) hydroelectric power plant basin, it may cause 60% of the reservoir silting. The GDS soil has also shown specific properties: 71% of the soil mass has a diameter of ~ 0.1 mm; there is a high rate of open macro-pores when the soil is dry (they close shortly after a moderate rainfall event ~ 40 mm); and it is prone to form gravel-like particles that silt in the reservoir delta (despite its fine diameter). Last, we observed that the check dams – as they were built – are not a sustainable solution: after a decade, nearly 10% are spilling due to the high siltation rates, causing dam-wall erosion and instability; and three dams have presented piping, with discharges (0.2 – 0.7 L.s-1) one thousand times higher than the expected percolation flow through the dams.

How to cite: de Araújo, J. C., Simplício, A. Á., Pereira, F. J., and Gomes Costa, C. A.: Erosion assessment in the desertification site of Gilbues, Brazil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1432, https://doi.org/10.5194/egusphere-egu2020-1432, 2019.

D2177 |
EGU2020-9571
Enrico Balugani, Andrea Rava, and Diego Marazza

Soil degradation through erosion is a major issue on a global scale, especially as the pressure on soils increases with increasing population, changing diets, and increase in land use changes. Measurements are plot specific and expensive, so most of the erosion assessment are done through modelling. The most used model for estimating soil water erosion worldwide is the Revised Universal Soil Loss Equation (RUSLE), which is an “ensemble” model with semi-empirical factors that can be determined using different equations, depending on scale of interest, geographical location, data availability. The –joint Research Centre (JRC) uses RUSLE to estimate water erosion potential in EU using spatial datasets collected by the European Soil Data Centre (ESDAC), as explained in a series of published articles. Model sensitivity analyses are a powerful tool for analysts and policy makers, especially for empirical and semi-empirical models like RUSLE, to assess model robustness, factor prioritization, and variance cutting. A sensitivity analysis was conducted on RUSLE by Estrada-Carmona et al. (2017) on a global (dishomogenous) parameter space using a Random Forest approach to calculate the relative relevance index. However, sensitivity analyses are dependent on the extent of the parameter space analysed and, especially for non-linear non-additive models like RUSLE, variance based methods are usually preferred.

Therefore, we performed a global sensitivity analysis of the RUSLE model as used by the JRC, using variance based methods and over the parameter space of the EU. The objective were to: (a) check the robustness of RUSLE in the EU parameter space, (b) define the most relevant factors on which to concentrate the attention (policy assessment) and (c) assess the interaction between these factors.

We analysed the spatial data provided by ESDAC to define the probability distribution of the model factors (the parameter space). We then sampled the parameter space with a low-discrepancy method and run the model on the whole dataset. We used the model output to: (a) plot the behaviour of the model to changes in single factors with scatterplots, (b) calculate the variance sensitivity index first order, (c) calculate the total sensitivity order, (d) analyse the relevant interactions between factors, first looking at the sensitivity indices, then using visual methods to show the model behaviour.

The results show that the C factor has the greater influence on the erosion estimates, followed by R and Kst, accounting for ~0.35, ~0.21 and ~0.0.04 of the erosion estimates variance, respectively. This is especially interesting, since it is possible to act on C and, hence, control erosion processes. The dependence on R, however, is troubling, since its average value will probably increase in time due to climate change. Kst can be affected only partially by increasing soil organic matter or soil stoniness. The analysis of the total effects show that C, R and Kst are all interacting between them. The P factor seems hardly relevant at this scale, hence it could be simply fixed, something already done in some studies, e.g. Gianinetto et al. 2019.

How to cite: Balugani, E., Rava, A., and Marazza, D.: Variance based sensitivity analysis of the RUSLE model in the E.U. parameter space, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9571, https://doi.org/10.5194/egusphere-egu2020-9571, 2020.

D2178 |
EGU2020-17768
Maire Holz and Jürgen Augustin

Soil erosion has for a long time been considered as a process causing soil organic matter (SOM) loss, however, recent studies pointed out that erosion may increase soil carbon sequestration because only 10-30% of eroded topsoil material is transported into water bodies while the remaining 70-90% are transported in depositional settings. Soil erosion leads to variation in topsoil thickness and soil characteristics and leads to two different main types of erosion states develop along hillslope: the eroding and the depositional landform position. Disruption of aggregates and the transport of soil during erosion, likely leads to SOM loss in the eroding slope. In contrast, after deposition, the eroded material can be protected if it is incorporated into soil aggregates or sorbed to mineral surfaces, leading to an increase in SOM in the depositional landform position.

So far, there has been no study evaluating literature results on the effect of erosion on carbon and nutrient distribution in soils. We therefore reviewed the literature for the influence of erosion on carbon/nutrient contents and stocks in erosion affected landscapes. While 32 studies reported results on the enrichment of eroding sediments in carbon (C), nitrogen (N) and phosphorus (P), 39 studies reported results on carbon/nutrient contents and stocks in erosion affected landscapes.

The average C enrichment ratio (sediment C/soil C) was 1.56 while N enrichment ratio was 1.54 and P-enrichment ratio was 1.77. This indicates that the fine soil fractions, that carbon and nutrients are mostly associated to, were preferentially moved during soil erosion. High element contents in the original soils, resulted in relatively low enrichment ratios which may allow the conclusion that in low C- and nutrient soils, a relatively high portion of the elements are stored in the fine soil fraction. C and N enrichment ratios showed a significant positive relation (R2=0.61), pointing to the strong ecological link of both elements.

Carbon and nutrient contents were comparable for all landscape positons (upslope, backslope, footslope, depositional). This indicates that carbon and nutrients, lost during an erosion event, are replenished relatively fast in the eroded slopes. In contrast, erosion induced C, N and P stocks increased from the upper towards the depositional soil site, resulting in a 1.6, a 1.4 and 2.2 time increase in C, N and P stocks for the depositional site, compared to the upslope position.

In conclusion, this meta-analysis indicates that carbon and nutrients are preferentially moved during soil erosion which might lead to loss in soil fertility and crop productivity after erosion events. However, similar C and nutrient contents along hillslopes indicate that elements are replenished relatively fast in eroded soils after the occurrence of an erosion event. Increased soil stocks toward the depositional site can therefore be explained by increased soil depths in lower hillslope positions. Changes in soil depth, rather than changes in C and nutrient contents are therefore more likely to explain soil fertility losses in eroding slopes compared to depositional sites.

 

How to cite: Holz, M. and Augustin, J.: Erosion effects on soil carbon and nutrient distribution: a meta-analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17768, https://doi.org/10.5194/egusphere-egu2020-17768, 2020.

D2179 |
EGU2020-5103
Nives Zambon, Lisbeth Lolk Johannsen, Peter Strauss, Tomáš Dostál, David Zumr, Thomas A. Cochrane, and Andreas Klik

Soil erosion by water is globally the main soil degradation process which leaves serious consequences on agricultural land and water aquifers. Splash erosion is the initial stage of soil erosion by water, resulting from the destructive force of rain drops acting on soil surface aggregates. Splash erosion studies conducted in laboratories use rainfall simulators. They produce artificial rainfall which can vary according to type of the rainfall simulator. In this study the aim was to quantify the differences in splash erosion rates affected by rainfall produced by two different rainfall simulators on two silt loam and one loamy sand soil. Splash erosion was measured using modified Morgan splash cups and the rainfall simulators were equipped with four VeeJet or one FullJet nozzle. The soil samples placed under simulated rainfall were exposed to intensity range from 28 to 54 mm h-1 and from 35 to 81 mm h-1, depending on the rainfall simulator. Rainfall characteristics such as drop size and velocity distribution were measured with an optical laser disdrometer Weather Sensor OTT Parsivel Version 1 (Parsivel) by OTT Messtechnik. Rainfall simulator with VeeJet nozzles produced smaller drops but higher drop velocity which resulted in higher kinetic energy per mm of rainfall compared to rainfall simulator with FullJet nozzles. For the same intensity rate measured kinetic energy under the rainfall simulator with VeeJet nozzles was 45% higher than rainfall kinetic energy from rainfall simulator with FullJet nozzles. Accordingly, the average splash erosion rate was 45 and 59% higher under the rainfall simulator with VeeJet nozzles for one silt loam and loamy sand soil, respectively. Splash erosion was found to be a linear or power function of the rainfall kinetic energy, depending on rainfall simulator. The obtained results highlight the sensitivity of the splash erosion process to rainfall characteristics produced by different rainfall simulators. The heterogeneity of rainfall characteristics between different types of rainfall simulators makes a direct comparison of results obtained from similar erosion studies difficult. Further experiments including comparison between more rainfall simulators could define influencing rainfall parameters on splash erosion under controlled laboratory conditions.

How to cite: Zambon, N., Lolk Johannsen, L., Strauss, P., Dostál, T., Zumr, D., A. Cochrane, T., and Klik, A.: Splash erosion experiments with silt loam and loamy sand soil under simulated rainfall produced by two types of rainfall simulators , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5103, https://doi.org/10.5194/egusphere-egu2020-5103, 2020.

D2180 |
EGU2020-3689
| Highlight
Paolo Tarolli, Eugenio Straffelini, Chiara Maria Mattiello, and Aldo Lorenzoni

Cultivating in high-steep slope hilly and mountainous landscapes, requires a great effort in terms of economic and human resources, especially if the territory is particularly complex from a geomorphological point of view and historically affected by landslides such as the Italian peninsula. This fragility is also combined with two other factors. The first is linked to agricultural mechanization, which causes soil compaction and a consequent alteration of its draining capacity. The second is related to climate change, responsible for an increase of extreme rainfall events characterized by intense, shorter and localized precipitations. The combination of these elements makes agricultural terraced landscapes at risk and prestigious vineyards, particularly important for historical, cultural, landscaping and economic reasons, increasingly sensitive to soil erosion processes.

In response to these problems, the project SOiLUTION SYSTEM is proposed (www.soilutionsystem.com),  aiming to identify an integrated system of environmentally and economically sustainable interventions able to reduce the risk of erosion and improve soil management in the terraced area of Soave (Veneto region), one of the two Italian GIAHS-FAO site. Indeed, in such terraced areas, the hydrogeological risk is high due to the steep-slope where heroic vineyards are cultivated. The project is also focused on multidisciplinary, capable of combining expertise from the academic world, farmers and other stakeholders, in order to promote a sustainable production approach to ensure greater soil resilience, as well as to protect biodiversity.

In the first phase, several terraced study areas historically threatened by erosion have been selected. Within them were organized topographic surveys using a low-cost commercial drone in combination with an RTK-GPS for the 3D reconstruction of the terrain using the Structure-From-Motion photogrammetric technique. The point cloud obtained was subsequently processed, filtered and interpolated in order to create high-resolution digital terrain models (DTM) with cells of resolution less than 50cm. Based on the obtained data, some geomorphological indicators were calculated to identify areas potentially susceptible to erosion. In order then to understand the processes that take place at a larger scale than the single areas detected by drone, geomorphological analyses were also performed on a 1m DTM elaborated from airborne LIDAR data, granted by the Italian Ministry for Environment, Land and Sea (MATTM).

The goals of the project are 1) to provide innovative survey techniques using low-cost commercial drone to better understand erosion processes in vineyards; 2) to install innovative tools for the monitoring of surface runoff in the field; 3) to test new mechanization prototypes with low impact on the soil and able to work on steep slopes; 4) to provide an innovative technique for the consolidation of dry stone walls; 5) to introduce the “conservative agriculture” for improving soil management; 6) to analyze the role of native herbaceous species as grass cover in erosion reduction; 7) to evaluate the efficiency of the proposed management model in considering biodiversity conservation purposes.

How to cite: Tarolli, P., Straffelini, E., Mattiello, C. M., and Lorenzoni, A.: SOiLUTION SYSTEM: innovative solutions for soil erosion risk mitigation and better management of vineyards in hills and mountain landscapes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3689, https://doi.org/10.5194/egusphere-egu2020-3689, 2020.

D2181 |
EGU2020-1471
Jay Le Roux and Bennie Van der Waal

Gully erosion can reach alarming dimensions and contribute significantly to soil loss and sediment yield in a catchment.  Since restoration resources are usually limited, strategic information on sensitive and erosion susceptible areas are needed to avoid future degradation.  Although the mapping of areas susceptible to gully formation is not a new concept, this study has potential in the Mzimvubu River Catchment, the only large river network in South Africa without a large reservoir.  The Tsitsa tributary’s catchment, where two large reservoirs are planned, consists of large areas of highly erodible soils with widespread gully erosion evident.  It is important to prevent further gully erosion in the catchment due to the presence of duplex and dispersive soils. Therefore, this study modelled areas that are susceptible to gully development in the Tsitsa River Catchment, as well as estimated the sediment yield potential from the susceptible areas if gully development occurs.  This was achieved by mapping gully-free areas in a GIS that have the same DEM-derived topographical variables, soil associations and land cover than gullied areas, followed by scenario analysis of the potential sediment yield.  More than 30 000 ha (7%) of the catchment is intrinsically susceptible to further gully development, consisting of drainage paths with a large contributing area and erodible duplex soils.  If not protected, these susceptible areas could contribute an additional 300 million m3 of sediment to the river network, reducing the volumes of both reservoirs by more than 50%. 

How to cite: Le Roux, J. and Van der Waal, B.: Gully erosion susceptibility modelling for avoided degradation planning, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1471, https://doi.org/10.5194/egusphere-egu2020-1471, 2019.

D2182 |
EGU2020-9285
| Highlight
Matthias Vanmaercke, Yixian Chen, Sofie De Geeter, Jean Poesen, and Benjamin Campforts

Gully erosion has been recognized as a main driver of soil erosion and land degradation. While numerous studies have focussed on understanding gully erosion at local scales, we have very little insights into the patterns and controlling factors of gully erosion at a global scale. Overall, this process remains notoriously difficult to simulate and predict. A main reason for this is that the complex and threshold-dependent nature of gully formation leads to very high data requirements when aiming to simulate this process over larger areas.

Here we help bridging this gap by presenting the first data-driven analysis of gully head densities at a global scale.  We developed a grid-based scoring method that allows to quickly assess the range of gully head densities in a given area based on Google Earth imagery. Using this approach, we constructed a global database of mapped gully head densities for currently >7400 sites worldwide. Based on this dataset and globally available data layers on relevant environmental factors (topography, soil characteristics, land use) we explored which factors are dominant in explaining global patterns of gully head densities and propose a first global gully head density map.

Our results indicate that there are ca. 1.7 to 2 billion gully heads worldwide. This estimate might underestimate the actual numbers of gully heads since ephemeral gullies (in cropland) and gullies under forest remain difficult to map. Our database and analyses further reveal clear regional patterns in the presence of gullies. Around 27% of the terrestrial surface (excluding Antarctica and Greenland) has a density of > 1 gully head/km², while an estimated 14% has a density of > 10 gully heads/km² and 4% has even a density of > 100 gully heads/km². Major hotspots (with > 50 gully heads/km²) include the Chinese loess plateau, but also Iran, large parts of the Sahara Desert, the Andes and Madagascar. In addition, gully erosion also frequently occurs (with typical densities of 1-50 gully heads/km²) in the Mid-West USA, the African Rift, SE-Brazil, India, New-Zealand and Australia.

These regional patterns are mainly explained by topography and climate in interaction with vegetation cover. Overall, the highest gully densities occur in regions with some topography and a (semi-)arid climate. Nonetheless, it is important to point out that not all gully heads are still actively retreating. Building on earlier insights into the magnitude and controlling factors of gully head retreat rates, we explore what our current results imply for assessing actual gully erosion rates at a global scale.

How to cite: Vanmaercke, M., Chen, Y., De Geeter, S., Poesen, J., and Campforts, B.: A first data-driven gully head density map of the world, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9285, https://doi.org/10.5194/egusphere-egu2020-9285, 2020.

D2183 |
EGU2020-3536
| Highlight
Mike Kirkby

The dominant direct physical processes responsible for desertification are water erosion, wind erosion and salinization.  Other threats that degrade the soil  include loss of biodiversity, loss of soil organic matter, fire, changing water resources, soil compaction, soil sealing and contamination. Soil management inevitably combines  human and physical effects.  Climate, which is the most important driver of the physical systems, is now being rapidly modified by human action, and at a scale which is much coarser than any local remedial action. 

  

In a model of near-subsistence systems, productivity is limited by climate and available labour, with some options for additional inputs through improved seed, fertilizer or tillage equipment. Optimum solutions in a particular environment depend on both climate and access to markets.  Agricultural surpluses, if any, allow investment in infrastructure – some of it directly  supporting agriculture through irrigation and market systems, some less directly useful through, for example, warfare or pyramid building.

 

Today some traditional drivers of desertification may no longer be relevant, as land, particularly in the global South, is grabbed for intensive irrigated farming, and populations move into mega-cities. The dominant drivers may become soil sealing around cities and transfers of urban and irrigation water.  In semi-arid areas this will lead to competition for the best land – for urban expansion and agricultural land with irrigation potential.  Desertification then becomes an issue increasingly focussed on abandoned marginal land, maintaining biodiversity, managing regional water resources and controlling erosion in the face of global climate change.

How to cite: Kirkby, M.: Desertification and Development: some broader contexts, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3536, https://doi.org/10.5194/egusphere-egu2020-3536, 2020.

D2184 |
EGU2020-12814
Andrey Zhidkin, Mikhail Komissarov, and Evgeny Zazdravnykh

We used the data from field surveys with more than 2500 soil sampling points at 4 research sites in various regions of Russia. The study sites are located in the European part of Russia in the most contrasting physical-geographical and socio-historical conditions of soil erosion: in the Moscow, Kursk, Belgorod regions and in the Republic of Bashkortostan. The digital modeling was carried out with using of the WATEM / SEDEM model based on digital elevation models of detailed scale (1:10 000) on a total area more than 2000 km2. An analysis of the sediment balance in small catchments showed, that the digital modeling of soil erosion (in case of a certain quality level of input parameters) at an acceptable level reflects on the average long-term erosion rates in the valley-beam relief. The authors developed an original method in soil erosion mapping. It consists in revealing statistical relationships between the calculated erosion rates by WATEM / SEDEM model and the actual data of soils humus horizons thicknesses. Based on these dependencies, the probability of participation of soils with varying degrees on erosion in each pixel is calculated.

The specific in formation of soil erosion at the Moscow region is largely due to the complex stage history of agricultural land development. For this key site, a detailed study of historical maps was carried out (with digitization in the GIS of the sites boundaries with a different land use history) for 8 periods, starting from 1797 to the present. Also, the history of crop rotation was studied in detail. Based on the analysis of maps and digital modeling of erosion-accumulation processes in this territory, a very high dynamics of arable land and soil erosion over the past few centuries was revealed, which significantly influenced on the formation of soil cover. At research sites in the Belgorod and Kursk regions, the features in formation of erosion-accumulative soil cover structures are due to the large area of agricultural land development. The comparison of soil cover erosion maps produced in accordance to the traditional method and the author’s approach is revealed a high convergence of results and the perspective of digital modeling using. The indisputable advantage of the digital method is the ability to formalize the procedure for assessing soil erosion, minimizing the contribution of subjective factors. Detailed studies in the Republic of Bashkortostan revealed the features in the formation of soil erosion  due to the developed denudation processes and karst microrelief. A detailed mapping of the soil cover and topographic mapping of the relief in key areas was carried out. It was revealed, that the using of a digital elevation model with very high accuracy (scale 1: 1000 and higher) allows to qualitatively simulate and estimate the rates of erosion and accumulation even in conditions of pronounced karst microrelief.

Acknowledgement
This research was supported by the Russian Foundation for Basic Research (RFBR) within the scientific project No. 18–35–20011.

 

How to cite: Zhidkin, A., Komissarov, M., and Zazdravnykh, E.: The joint application of digital modeling and field soil survey data for improvement of the accuracy in soil erosion mapping, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12814, https://doi.org/10.5194/egusphere-egu2020-12814, 2020.

D2185 |
EGU2020-7985
Selen Deviren Saygin, Fikret Ari, Cagla Temiz, Sefika Arslan, Mehmet Altay Unal, and Gunay Erpul

Rill erodibility (Kr), which is a measure of the resistance of soil particles against disintegration in a rill under concentrated flow conditions, is a significant characteristic for rill initiation in a field.  The Process-based WEPP (Water Erosion Prediction Project) originally models Kr by linear excess shear stress (τ), and it is mostly obtained from mini-flume experiments at laboratory conditions. Alternatively, a critical value of flow stress (τcr) that points to fragmentation in rills can be modeled by a fluidized bed approach that quantifies the conditions in terms of cohesion (Co) and flow velocity (Vf) by considering the soil as a cohesive material. In there, the water as a fluid applies pressure on solid particle proportional to flow rate of the fluid (v). But, performed related studies on it were mostly tested for the limited soil types. The objectives of this study were to test these relationships and model the rill characteristic for the heavy textures of different soil types and investigate the role of basic soil properties on rill initiation. Experimental results showed that the stronger regression coefficient (R2=0.78) was found between Kr and flow velocity (Vf) monitored at the fluidization stage than that between Co & τcr at the studied soil conditions. However, correlations between constant and dynamic soil properties and the measured Kr, τcr, Co and Vf values were also quite remarkable (p<0.01) for next-generation modeling studies in terms of rill dynamics. It is believed that the fluidized-bed approach has a great potential to model Kr and encouragingly it is worth to be tested with wider data-sets under different soil-moisture conditions.

Keywords: Rill erodibility, Soil Cohesion, Fluidized bed approach, WEPP

How to cite: Deviren Saygin, S., Ari, F., Temiz, C., Arslan, S., Unal, M. A., and Erpul, G.: Fluidized-bed: As an alternative method for rill erodibility modeling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7985, https://doi.org/10.5194/egusphere-egu2020-7985, 2020.

D2186 |
EGU2020-13575
Pasquale Borrelli, Richard Cruse, Brian Gelder, and Panos Panagos

Over the last two decades, geospatial technologies such as Geographic Information System and spatial interpolation methods have facilitated the development of increasingly accurate spatially explicit assessments of soil erosion. Despite these advances, current modelling approaches in Europe rest on (i) an insufficient definition of the proportion of arable land that is exploited for crop production, (ii) a neglect of the intra‐annual variability of soil cover conditions in arable land, and (iii) offer little understanding of the spatio-temporal trends of soil erosion. Here, we represent the recent developments of two methods tested to overcome current limitations and move towards the implementation of new modelling approaches in Europe.

The Object-oriented Soil Erosion Modelling and Monitoring v2.0 (O-SEMM) (Land degradation & development, 29, 1270-1281, 2018) combines highly accurate agricultural parcel information systems (LPIS) with crop statistics, Landsat 8 and Sentinel 2 satellite data and high temporal resolution rainfall data to assess soil erosion events at parcel level.

The Daily Erosion Project (DEP) (Earth Surface Processes and Landforms, 43, 1105-1117, 2018), developed by the Iowa State University, estimates soil erosion and water runoff occurring on hill slopes using the WEPP erosion prediction model.

References

Borrelli, P., Meusburger, K., Ballabio, C., Panagos, P., & Alewell, C. (2018). Object‐oriented soil erosion modelling: A possible paradigm shift from potential to actual risk assessments in agricultural environments. Land degradation & development, 29(4), 1270-1281.

Gelder, B., Sklenar, T., James, D., Herzmann, D., Cruse, R., Gesch, K., & Laflen, J. (2018). The Daily Erosion Project–daily estimates of water runoff, soil detachment, and erosion. Earth Surface Processes and Landforms, 43(5), 1105-1117.

How to cite: Borrelli, P., Cruse, R., Gelder, B., and Panagos, P.: Object‐oriented Soil Erosion Modelling and Daily Erosion Project: Laying the foundation for a new generation of soil erosion assessments in Europe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13575, https://doi.org/10.5194/egusphere-egu2020-13575, 2020.

D2187 |
EGU2020-97
Safwan Mohammed

Soil erosion by water is a serious problem in the coastal region of Syria. Annually, a hundred tons of soil are eroded from different ecosystems in the study area. Recently, The USDA-WEPP (Water Erosion Prediction Project erosion model) was widely used to estimate soil loss by water erosion. Unfortunately, detailed studies about the WEPP-model performance in the eastern Mediterranean in general and Syria, in particular, are still lacking. Within this context, this research undertook an assessment of the WEPP-model performance in the coastal region of Syria.

The study area is characterized by complex topography (slope ranges between 2% and 45%), heavy precipitation within short time intervals, and mixed land cover. On other hand, the most exposed ecosystems to soil erosion are agricultural (AG), burned forest (BF) and forest (FO). For this reason, experimental plots with 3 replicants in 9 different representative locations for each ecosystem were set up (81 experimental plots in total) to measure soil erosion by water. In the next step, the WEPP input files were prepared and run for each location. Finally, the WEPP performance was tested by using four statistical indexes: Pearson's correlation coefficient (r), the Nash-Sutcliffe coefficient (NSE), the percent bias (PBIAS), and RSR (the ratio of root mean square error (RMSE) to the standard deviation of the measured data).

The results showed that observed soil erosion ranges between 32 ton/h/year and 165 ton/h/year in the AG, while it ranges from 3 ton/h/year to 8 ton/h/year in the FO. Similarly, WEPP results range between 32 ton/h/year and 152 ton/h/year in the AG, while they range from 1.4 ton/h/year to 15 ton/h/year in the FO. The model performance showed a good agreement between measured and estimated values for AG systems (R =0.96, NSE=0.84; RSR=0.39; PBAIS=13.05), and a less satisfactory one for both forest and burned forest.

How to cite: Mohammed, S.: Sediment Yield Modeling in The Coastal Region of Syria Using the WEPP-Model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-97, https://doi.org/10.5194/egusphere-egu2020-97, 2019.

D2188 |
EGU2020-217
Philipp Saggau, Michael Kuhwald, and Rainer Duttmann

Soil erosion by water is recognized as the most threatening land degradation process worldwide, reducing natural soil fertility and productivity especially on arable land. Despite advances in soil erosion modelling, one major process, which is rarely investigated, is the effect of soil compaction from field management induced wheel tracks. However, tramlines noticeably contribute to the amount of soil eroded inside a field. To quantify these effects we incorporate high-resolution spatial tramline data into modelling. For simulation, we used the process-based soil erosion model EROSION3D, which has been applied on different fields for a single rainfall event. Model results were compared against measured soil loss. Our investigation showed that i) grid-based models like E3D are able to integrate tramlines, ii) the share of measured erosion between tramline and cultivated areas fits well with measurements for resolution ≤ 1 m, iii) tramline erosion showed a high dependency to the slope angle and iv) soil loss and runoff are generated quicker within tramlines during the erosion event. The results indicate that the integration of tramlines in soil erosion modelling improves the spatial prediction accuracy, and therefore, can be important for soil conservation planning.

How to cite: Saggau, P., Kuhwald, M., and Duttmann, R.: Adopting soil properties of compacted tramlines into soil erosion modelling: A field-scale approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-217, https://doi.org/10.5194/egusphere-egu2020-217, 2019.

D2189 |
EGU2020-793
Rebeca Zavala, Israel Cantú, Laura Sánchez, Humberto González, Eduardo Estrada, and Tetsuya Kubota

In recent years, the effect of soil bioengineering has played a very important role on slope stability. However, our area of study is constantly under the influence of small-scale earthquakes and extreme events of heavy rainfall which cause potentially unstable conditions on the slopes. The mechanical properties of the root systems tensile strength (Ts) and modulus of elasticity (Eroot) of four native species were analyzed for a potential use as soil bioengineering elements. We investigated if tensile strength (N/mm2) and modulus of elasticity of roots (N/mm2) was different between studied species: Cercis canadensis, Celtis laevigata, Quercus rysophylla and Ligustrum lucidum. The species considered were selected based on their native characteristics and widespread existence on the slopes. Regarding tree forest species, the tests were conducted with the Universal Testing Machine Shimadzu type SLFL-100KN. The relationships among root diameter, tensile strength (Ts), and modulus of elasticity (Eroot) was negative and could be fitted with a power regression equation, showing highly significant   values p<0.01.Celtis laevigata showed the maximum value of tensile strength (Ts) 28.11 N/mm2 while the minimum value of tensile strength was observed in Ligustrum lucidum 5.27 N/mm2. For the variable modulus of elasticity (Eroot) Celtis laevigata  showed the maximum value of 90.01N/mm2 while the minimum value of modulus of elasticity was observed in Ligustrum lucidum 29.16 N/mm2.Results of mechanical proprieties are showed the following ascending order: Ligustrum lucidum < Quercus rysophylla < Cercis canadensis < Celtis laevigata. Likewise, Celtis laevigata showed the highest tensile strength and modulus of elasticity of all investigated species.

 

Key words: root, tensile strength, modulus or elasticity.

 

 

How to cite: Zavala, R., Cantú, I., Sánchez, L., González, H., Estrada, E., and Kubota, T.: Mechanical Properties of Native Tree Species for Soil Bioengineering in Northeastern Mexico, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-793, https://doi.org/10.5194/egusphere-egu2020-793, 2019.

D2190 |
EGU2020-863
Filippo Milazzo, Tom Vanwalleghem, Pilar Fernández, Rebollo, and Jesus Fernández-Habas

Land use and land management changes impact significantly on soil erosion rates. The Mediterranean, and in particular Southern Spain, has been affected by important shifts in the last decades. This area is currently identified as a hotspot for soil erosion by water. In the effort to achieve the SDG Target 15, we aim to show the effect of land management change, assessing soil erosion rate based on historical data. We analyzed the evolution of land use from historical aerial photographs between 1990 and 2018. We then calculated soil erosion with RUSLE. For this, we first determined the distribution frequency of cover-management factors for each land use class, comparing current land use maps with the European Soil Erosion Map (Panagos et al., 2015). Past C factors where then assigned using a Monte Carlo approach, based on the obtained frequency distributions. 

How to cite: Milazzo, F., Vanwalleghem, T., Fernández, Rebollo, P., and Fernández-Habas, J.: Evaluation of changes in soil erosion rates in Andalucia between 1990 and 2018, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-863, https://doi.org/10.5194/egusphere-egu2020-863, 2019.

D2191 |
EGU2020-969
Daria Fomicheva and Andrey Zhidkin

Digital modeling of soil erosion has been actively developed in recent decades, including for solving practical problems of agriculture. This paper presents a new approach to mapping the degree of erosion of the soil cover based on a detailed retrospective analysis of the history of land use over the last 300 years.

The study site is located in the Moscow region, characterized by a stage history of plowing. The analysis of the boundaries of arable land was carried out using the digitization of maps for 1797, 1860, 1871, 1931, 1954, 1985, 2000 and 2018 years.

Erosion processes were simulated using the WATEM / SEDEM. LS factor was calculated based on a digital elevation model based on the digitized detail topographic map. Soil erodibility factor was calculated according to the formula [1] based on our own analytical data on soil properties (K=0.065–0.090 kg*h*MJ-1mm-1). The rain erosivity factor was taken from the [2]. The crop erosivity factor was taken from regional data, taking into account a detailed analysis of the history of crop rotation.

Soil erosion was calculated for each of 8 periods. Estimated rates were multiplied by the duration of the periods. The soil loss volumes were summarized using the raster calculator. The authors have database of soil surveys at 1567 points. The obtained estimated long-term volumes of soil loss were correlated with the data of a field survey of soils. Based on the obtained dependencies between the calculated soil loss volumes and the field survey data, a map of the erosion soil cover structures was constructed.

In the territory, the volume of soil loss varied from 0.02 tons to 1170 tons. The average volume of soil loss over 300 years was about 63.33 tons. It was revealed that the volume of soil loss is determined not only by the area of ​​arable land, but also by the location and topography of the plowed plots and the composition of crop rotation. The most intense erosion was observed in the first decades after the abolition of serfdom law (after 1860).

Despite the long period of land use, the soil cover of the study area is not very eroded, primarily due to the low erosion potential of the relief. However, the territory is divided into sections, to a different degree, transformed by soil erosion due to plowing of different duration and the composition of crop rotation.

This work was supported by the Russian Foundation for Basic Research (project for young scientists no. 18-35-20011)

[1] Renard K., Foster G., Weesies G., McCool D., Yoder D. (1997) Predicting soil erosion by water: a guide to conservation planning with the Revised Universal Soil Loss Equation (RUSLE). USDA Agriculture Handbook â„–703, 384 p.

[2] Panagos P, Borrelli P, Meusburger K, et al. Global rainfall erosivity assessment based on high-temporal resolution rainfall records. Sci Rep. 2017;7(1):4175.

How to cite: Fomicheva, D. and Zhidkin, A.: Digital modeling of erosion soil cover patterns development over the last 300 years (Moscow region, Russia), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-969, https://doi.org/10.5194/egusphere-egu2020-969, 2019.

D2192 |
EGU2020-1227
leichao bai

The magnitude of soil erosion and sediment reduction efficiency of check dams under extreme rainstorms are long-standing concerns. This paper aims to use check dams to deduce the amount of soil erosion under extreme rainstorms in watersheds and to identify the difference of sediment intercepting efficiency of different types of check dams. Based on the sediment deposition of 12 check dams with 100% sediment intercepting efficiency and sub-catchment clustering by taking 12 check dams-controlled catchments as standard separately, the amount of soil erosion caused by an extreme rainstorm event on July 26th, 2017 (named “7·26” extreme rainstorm) was deduced in the Chabagou watershed in the hill and gully region of the Loess Plateau. The differences of sediment intercepting efficiency among check dams in the watershed were analysed according to the field observation 17 check dams. The results showed that the average erosion intensity under the ‘7·26’ extreme rainstorm was approximately 2.03×104 t·km-2, which was 5 times that in the second erosive rainfall in 2017 (4.15×103 t·km-2) and 11-384 times that in 2018 (0.53×102 t·km-2 - 1.81×103 t·km-2). Under the ‘7·26’ extreme rainstorm, the amount of soil erosion in the Chabagou watershed above Caoping hydrological station was 4.20×106 tons. The sediment intercepting efficiencies check dams with drainage canals (including the destroyed check dams) and with drainage culverts was 6.48% and 39.49%, respectively. The total actual sediment amount trapped by the check dam was 1.11×106 tons, accounting for 26.36% of the total soil erosion amount. In contrast, 3.09×106 tons of sediment was inputted to the downstream channel, and the sediment deposition in the channel was 2.23×106 tons, accounting for 53.15% of the total amount of soil erosion. The amount of sediment transport at the hydrological station was 8.60×105 tons. The sediment delivery ratio (SDR) under the “7·26” extreme rainstorm was 0.21. The results indicated that the amount of soil erosion was huge, and the sediment intercepting efficiency of check dams was greatly reduced under extreme rainstorms. It is necessary to strengthen the management and construction technology standards of check dams to improve the sediment intercepting efficiency and flood safety in the watershed.

How to cite: bai, L.: Soil erosion and sediment interception by check dam in watershed under extreme rainstorm on the Loess Plateau, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1227, https://doi.org/10.5194/egusphere-egu2020-1227, 2019.

D2193 |
EGU2020-1694
Changjia Li and Chengzhong Pan

Although numerous studies have acknowledged that vegetation can reduce erosion, few process-based studies have examined how vegetation cover affect runoff hydraulics and erosion processes. We present field observations of overland flow hydraulics using rainfall simulations in a typical semi-arid area in China. Field plots (5 m × 2 m) were constructed on a loess hillslope (25°), including bare soil plot as control and three plots with planted forage species as treatments—Astragalus adsurgens (A. adsurgens), Medicago sativa (M. sativa) and Cosmos bipinnatus (C. bipinnatus). Both simulated rainfall and simulated rainfall + inflow were applied. Forages reduced soil loss by 55–85% and decreased overland flow rate by 12–37%. Forages significantly increased flow hydraulic resistance expressed by Darcy-Weisbach friction factor by 188–202% and expressed by Manning’s friction factor by 66–75%; and decreased overland flow velocity by 28–30%. The upslope inflow significantly increased overland flow velocity by 67% and stream power by 449%, resulting in increased sediment yield rate by 108%. Erosion rate exhibited a significant linear relationship with stream power. M. sativa exhibited the best in reducing soil loss which probably resulted from its role in reducing stream power. Forages on the downslope performed better at reducing sediment yield than upslope due to decreased rill formation and stream power. The findings contribute to an improved understanding of using vegetation to control water and soil loss and land degradation in semi-arid environments.

How to cite: Li, C. and Pan, C.: Overland runoff erosion dynamics on steep slopes with forages under field simulated rainfall and inflow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1694, https://doi.org/10.5194/egusphere-egu2020-1694, 2019.

D2194 |
EGU2020-3369
Zhenyu Lv, Tianling Qin, Hanjiang Nie, and Jianwei Wang

Abstract: Soil management practices, such as Terrace (TE), Contour Ridge (CR), Conservation Tillage (CT), Green Manure (GM) and Straw Mulching (SM), have been widely applied all over the word, due to their positive effects on enhancing Water Storage Capacity (WSC for short) of soil and improving the effectiveness of local precipitation.  However, there are few studies focus on the assessment of WSC of soil management practices in basin scale. In this study, a series of empirical equations for evaluating the WSC of different types of soil management practices were established, based on the fundamental assumption of SCS-CN model, and the geometric parameters of TE and CR. Taking the Sihe River Basin as an example, the current construction area of soil management practices and the potential of the design scenarios were input into the equations, to calculate the existing and potential WSC of various soil management practices. The results show that the construction area of soil management practices in the basin was 679.73 km2 in 2015, and the WSC reached 61.85 Million m3. Thereinto, the WSC of the SM was the largest, which was 19.83 Million m3; that of the GM was the smallest, which was 2.08 Million m3. The total potential construction area of soil management practices in each design scenario was 1797.13 km2. Scenario I gave priority to the TE and the CR construction, the WSC of soil management practices in the basin was 174.84 Million m3, which was 182.68% higher than that of in 2015. The WSC of soil management practices in Scenario II who gave priority to the SM, CT and CR construction, was 171.84 Million m3, which was 177.84% higher than that of in 2015. This research further compared the water storage efficiency of various soil management practices and discussed the uncertainty of the equations. The results could provide some references for integrated soil water management.

How to cite: Lv, Z., Qin, T., Nie, H., and Wang, J.: Evaluation of the water storage capacity of soil management practices in basin scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3369, https://doi.org/10.5194/egusphere-egu2020-3369, 2020.

D2195 |
EGU2020-6497
Tao Peng, Qianyun Cheng, and Le Cao

The development of karst landforms in southwest China has resulted in surface and underground dual hydrogeological structure. The characteristics of the mechanism of soil erosion and its environmental effects are different from those in non-karst regions. This study aims to monitor sediment load and identify the main sediment source in a typical karst plateau agroforestry catchment, to estimate the relative contribution rates of surface and underground river sediment sources. The results show that the annual sediment transport modulus in catchment is very low (5.1 Mg km-2 a-1) in this carbonate agroforestry catchment compare to deforestation 20 years ago (20 Mg km-2 a-1). Sediment Fluxes in the underground river and surface river account for 19.7% and 80.3% respectively. Soil leakage is an important way but not a main way of soil erosion in typical karst watershed. There is no obvious soil erosion on the hillsides (less than 1 Mg km-2 a-1), but the sediment sources results shows sediment sources of surface and underground river are different in 2017 and 2018, In 2017, it indicate that carbonate surface soil contributes 16.2% and 11.9% of the total suspended sediment to the surface and underground river respectively, and the clastic rock pieces are the primary source of both surface and underground river sediments, 79.5% and 60.8% respectively. Subsurface soil contributes a smaller fraction to the total sediment load, 4.3% to surface rivers and 27.3% to underground rivers. The 137Cs values for some suspended sediments in 2018 were outside the range all of the soil source samples, it attributed to re-mobilization of old sediment stored in karst underground conduits during the deforestation, and these “old sediments” could generate to the surface again when with the rainfall erosivity above 49 J·mm·m-2·h-1.

How to cite: Peng, T., Cheng, Q., and Cao, L.: Monitoring of suspended sediment load and Sediment Sources in a Karst Plateau Catchment of Southwest China., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6497, https://doi.org/10.5194/egusphere-egu2020-6497, 2020.

D2196 |
EGU2020-6578
Anthi Eirini Vozinaki, Dimitris Alexakis, and Ioannis Tsanis

Olive and vine orchards in the island of Crete suffer from extreme soil erosion due to intense rainfall, farm slope and/or the intensification of tilling processes. This research aims to assess the impacts of agricultural practices, land use, and vegetation cover on the quantity of erosion processes in three study areas located in Western Crete. These areas provide the case studies of soil loss (erosion/deposition) monitoring analysis and assessment process. Advanced research treatments of Soil Improving Cropping Systems (SICS) are implemented and tested in three different crop types: (1) Crop cover treatment (i.e. seed with vetch) applied in vineyards (Vitis vinifera) in Alikampos; (2) Tilled treatment applied in Olive orchards (Olea europaea cv. Koroneiki) in Astrikas; and (3) Crop switch treatment from Orange trees to Avocados applied in Koufos. It is notable that an avocado farm, besides providing financial benefits, can also maintain a superior overall soil quality. Soil erosion has not been measured yet for avocados, however, avocado plantations are proposed as a sustainable alternative. Soil loss is estimated for the aforementioned case studies, by comparing the results from treatments applied in SICS areas, with the Control areas, where no treatment has taken place. Three different methodologies are used in order to identify soil loss amount: (a) Sediment traps (all sites); (b) Cross sections measurement (Alikampos and Astrikas) and (c) Soil deposition reference sticks (Alikampos and Koufos). Preliminary results show that soil loss values (tn/ha), are absolute values of erosion/deposition, and range from 2.33 to 16.41 tn/ha for vineyards with no vetch (Control), from 1.64 to 13.46 tn/ha for vineyards with vetch (SICS), from 2.21 to 15.66 tn/ha for no tilled olive orchards (Control), from 0.43 to 5.8 tn/ha for tilled olive orchards (SICS), from 2.63 to 10.05 tn/ha for orange orchards (Control), and from 2.24 to 8.95 tn/ha for avocado orchards (SICS). In addition, the ongoing research has already yielded the following yearly average soil loss rates (tn/ha/yr): vineyards – Control 6.883 tn/ha/yr versus vineyards – SICS 6.587 tn/ha/yr; olive orchards -  Control 7.019 tn/ha/yr versus olive orchards – SICS 3.215 tn/ha/yr; and orange orchards – Control 6.406 tn/ha/yr versus avocados – SICS 5.386 tn/ha/yr. The above field results are also in general agreement with the yearly average soil erosion rates in the island of Crete, modeled by several researchers. All study sites show mitigation of soil loss and improvement of soil quality from the application of SICS treatments. Therefore, it is recommended to raise farmers’ awareness about their effectiveness in order to confront the consequences of soil degradation.

Keywords: Soil Loss; Sediment Traps; Soil Improving Cropping Systems; Crete

The research leading to these results is funded by H2020 program under grant agreement n° 633814 (SOILCARE).

How to cite: Vozinaki, A. E., Alexakis, D., and Tsanis, I.: Monitoring and Estimating Soil Loss in Agricultural Areas - Case Studies in Chania, Crete, Greece, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6578, https://doi.org/10.5194/egusphere-egu2020-6578, 2020.

D2197 |
EGU2020-8078
Dimitrios D. Alexakis, Christos Polykretis, and Manolis G. Grillakis

The regular patterns of soil erosion tend to change at different scales of observation, affecting the mechanism of soil erosion and its evolution characteristics. Fragmentation and land loss are two critical, interrelated processes that influence the entire landscape. In this study, we examine how the relationship between landscape fragmentation and soil loss is diversified in different scales and contexts. Thus, different Earth Observation (EO) products, in terms of spatial analysis, such as Landsat 8, Sentinel 2 and Planetscope imageries are utilized to search the influence of scale effect in fragmentation rate. Land use / Land Cover (LULC) maps were developed in different scales through the use of sophisticated classification algorithms. Following, FRAGSTATS software was employed to calculate spatial metrics in order to capture important aspects of landscape patterns such as edge density, largest patch index, number of patches, contagion etc. In this context we calculated fractal dimensions and Moran’s I spatial autocorellation statistics and used them to represent the degree of landscape fragmentation. Soil loss data, estimated in different scales were incorporated in the overall study as derived from RUSLE (Revised Universal Soil Loss Estimation) soil loss estimation model. Ordinary least square (OLS) and Geographical Weighted Regression (GWR) methodologies were applied in order to correlate both spatially and quantitavely soil loss rates with landscape fragmentation The results denoted the fact that areas of larger patches with least fragmentation suffer less from soil loss phenomena. The overall approach can be used as a road map in order to extract crucial conclusions about landscape’s diachronic evolution and how this is affected both from natural and anthropogenic interventions.

How to cite: Alexakis, D. D., Polykretis, C., and Grillakis, M. G.: Studying soil erosion rates through landscape fragmentation. A case study in Crete, Greece., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8078, https://doi.org/10.5194/egusphere-egu2020-8078, 2020.

D2198 |
EGU2020-15394
Michał Beczek, Magdalena Ryżak, Rafał Mazur, Agata Sochan, Cezary Polakowski, and Andrzej Bieganowski

Soil, i.e. the natural outer layer of the lithosphere and an important component of many ecosystems, may be subjected to various degradation processes dependent on different factors. One of the forms of degradation is water erosion, where the first stage is the splash phenomenon. This process is caused by water drops hitting the soil surface during rainfall, which results in detachment and ejection of splashed material and transport thereof over different distances. The aim of this study was to present the application of the high-speed camera technique for investigations of surface phenomena (effects) influenced by the impact of a single water-drop onto the soil surface.

The measurements were conducted on types of soil differentiated in terms of texture and variants of initial moisture content, which helped to observe different aspects of the soil splash phenomenon. Water drops with a diameter of 4.2 mm fell on soil samples with various kinetic energy values depending on the height of the drop fall (up to 7m). Phantom Miro M310 high-speed cameras were used to observe the effects of the drop impact. The devices registered images with a speed of 3260 fps (frames per second) at the highest available resolution (1280x800 pixels). The following phenomena were observed: I) ejection of splashed particles (including solid soil particles, water droplets, solid particles within the water sheath); II) crown formation – when the drop impacting onto wet soil surface forces the liquid layer to rise up and form a crown (important for the mode and amount of transferred material); III) micro-crater formation – the deformation of the surface and formation of a shallow pool after the drop impact.          

 

This work was partly financed from the National Science Centre, Poland; project no. 2018/31/N/ST10/01757.

 

References:

  1. Beczek M., Ryżak M., Sochan A., Mazur R., Bieganowski A.: The mass ratio of splashed particles during raindrop splash phenomenon on soil surface. GEODERMA 347, 40-48, 2019
  2. Beczek M., Ryżak M., Lamorski K., Sochan A., Mazur R., Bieganowski A.: Application of X-ray computed microtomography to soil craters formed by raindrop splash. Geomorphology 303, 357-361, 2018
  3. Beczek M., Ryżak M., Sochan A., Mazur R., Polakowski C., Bieganowski A.: The differences in crown formation during the splash on the thin water layers formed on the saturated soil surface and model surface. PLoS ONE 12, 2017

How to cite: Beczek, M., Ryżak, M., Mazur, R., Sochan, A., Polakowski, C., and Bieganowski, A.: The use of high-speed camera technique for observation of soil splash phenomena, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15394, https://doi.org/10.5194/egusphere-egu2020-15394, 2020.

D2199 |
EGU2020-21021
Rina Hu, Eerdun Hasi, and Jie Yin

 Desertification is one of the main environmental problems in arid and semi-arid areas. In Otindag sandy land, the activation of fixed sand dunes caused by climate change and human activities is the main reason of the development of desertification, and the activation of fixed sand dunes is first manifested by the formation and evolution of blowouts. In recent years, with the increase of high-resolution image data, it has become possible to make use of dynamic monitoring of terrain and landscape changes in small areas, so as to accurately analyze the interaction between terrains and influencing factors on smaller landscape scales, especially dune-interdune scale. We use the high-resolution satellite image data in 2010, 2013, 2016 and 2019 with the ground survey data as the data source, as well as the ArcGIS software to adopt the visual interpretation method. According to the different developmental positions, the shapes of the blowouts can be divided into saucer, bowl, groove, dustpan and irregular shaped. In the study area, the ways of changes in blowout are mainly based on expansion and amalgamation between 2010 and 2019. The area of blowout increased by 6.47hm2 from 2010 to 2013. During 2013-2016, the area increased by 4.89hm2, following by the next three years, it continued growing by 3.04hm2. With little disturbance of human activity, the growth of blowouts in this area is largely affected by the change of climate factors. As the dynamic factor of blowouts, the reduction in sand drift potential, only decreases the development rate and slows down the process. The shapes of the blowout themselves also work as the main influencing factor.

How to cite: Hu, R., Hasi, E., and Yin, J.: Dynamic changes of blowout in the fixed dune on the southeastern fringe of Otindag sandy land in recent decade, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21021, https://doi.org/10.5194/egusphere-egu2020-21021, 2020.

D2200 |
EGU2020-22440
Fahime Nikseresht and Schulin Rainer

Wind erosion is one of the main factors of soil degradation and air pollution in arid and semiarid regions. In recent years, dust storms have become ever more important sources of air pollution in large areas of Iran. Dust storms previously were confined to the summer season and to western Iran. Nowadays, dust storms occur during eight months of the year and extend to the central regions and the entire south of Iran. This is causing increasing problems for the residents of the affected areas, threatening their health and impairing social, economic and agricultural activities. Ahvaz, the capital of Khuzestan Province, is the city that is most seriously affected by these problems in Iran.

Wind erosion is a multifaceted phenomenon influenced by a variety of factors. One of these factors that has changed considerably in recent time in Iran is land use/cover and land management. To investigate the impact of these changes on wind erosion potential in southwestern Iran we applied an empirical model of the Iran Research Institute of Forest and Rangeland (IRIFR) to remote sensing data extracted from Landsat ETM+ and Landsat 8 imagery of 2010 and 2019. Relationships between changes in wind erosion and land use/cover were determined by cross-tabulation, combining the original spectral bands with synthetic bands and using Maximum Likelihood classification.

The results indicate major changes in wind erosion potential over the last decade in the study area. Interestingly, while areas with a low, medium, and high sediment yield potential decreased, areas with a very high sediment yield potential have increased. Increasing soil erosion potential was primarily related to the conversion of rangeland to agricultural cropland Moreover, the results indicate an increase in desertification in the study area which is also a clear evidence of increasing in soil erosion.

How to cite: Nikseresht, F. and Rainer, S.: Influence of changing land use/cover and land management on wind erosion potential in southwestern Iran, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22440, https://doi.org/10.5194/egusphere-egu2020-22440, 2020.

D2201 |
EGU2020-9661
Thomas Weninger, Nathan King, Karl Gartner, Barbara Kitzler, Simon Scheper, Peter Strauss, and Kerstin Michel

The degrading impact of wind on agricultural soils has been observed throughout centuries in the Pannonian region of central Europe. Nevertheless, soil loss was not yet quantified and the extent or relevance of the problem are unknown for this agriculturally important region. Especially dry soil surface is highly prone to erosion and as drought periods are expected to become more frequent and severe with changing climate, the risk of wind erosion will increase accordingly. Living windbreaks and similar agro-forestry systems are supposed to be highly effective measures against wind erosion. In an extensive research project, multiple approaches are integrated to obtain a broad view onto the relevance of soil degradation by wind on plot scale and its regional distribution.

More in detail, case studies are conducted where the soil loss by wind erosion is measured in sediment traps. Data about driving and stabilizing factors like wind speed, soil moisture, vegetation density etc. are measured in high spatial and temporal resolution. The measurements started in December 2019. Besides, wind erosion risk is modelled and mapped on regional scale applying state-of-the-art model procedures. The measurement results are used in an attempt to down-scale the model application and thus create a link to ground-truth data. Information about spatial and temporal variability of the driving factors is used for implementation of stochastic calculation procedures in a sensitivity study which determines the most relevant factors for wind erosion mitigation.

The used modelling approach also includes the effects of wind shelters what enables a partly evaluation of the existing network of such elements in the Pannonian region. There, the Authority of Land Reform has been supporting and documenting the installation of wind shelters for more than 60 years. Incorporating this data base, quantitative and qualitative statements will be developed about the state of the shelter belts and their relevance concerning erosion rates. Additionally, the potential and actual value of living windbreaks will be determined with special regards to physiological and ecological characteristics, stability under future climate conditions and further ecosystem services in agricultural landscapes.

How to cite: Weninger, T., King, N., Gartner, K., Kitzler, B., Scheper, S., Strauss, P., and Michel, K.: Linking regional modelling with field measurements to evaluate effectiveness of living windbreaks as measures against wind erosion, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9661, https://doi.org/10.5194/egusphere-egu2020-9661, 2020.