Editorial

4 pages, 188 KiB

Open AccessEditorial

Soil Water Erosion

by Csaba Centeri

Water 2022, 14(3), 447; https://doi.org/10.3390/w14030447 - 01 Feb 2022

Cited by 2 | Viewed by 1845

Soil erosion by water is considered to be one of the major forms of soil degradation (other than soil erosion by wind, acidification, salinization, desertification, etc [...] Full article

(This article belongs to the Special Issue Soil Water Erosion)

Research

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23 pages, 8177 KiB

Open AccessArticle

Estimation of Potential Soil Erosion and Sediment Yield: A Case Study of the Transboundary Chenab River Catchment

by Muhammad Gufran Ali, Sikandar Ali, Rao Husnain Arshad, Aftab Nazeer, Muhammad Mohsin Waqas, Muhammad Waseem, Rana Ammar Aslam, Muhammad Jehanzeb Masud Cheema, Megersa Kebede Leta and Imran Shauket

Water 2021, 13(24), 3647; https://doi.org/10.3390/w13243647 - 18 Dec 2021

Cited by 13 | Viewed by 3839

Abstract

Near real-time estimation of soil loss from river catchments is crucial for minimizing environmental degradation of complex river basins. The Chenab river is one of the most complex river basins of the world and is facing severe soil loss due to extreme hydrometeorological [...] Read more.

Near real-time estimation of soil loss from river catchments is crucial for minimizing environmental degradation of complex river basins. The Chenab river is one of the most complex river basins of the world and is facing severe soil loss due to extreme hydrometeorological conditions, unpredictable hydrologic response, and complex orography. Resultantly, huge soil erosion and sediment yield (SY) not only cause irreversible environmental degradation in the Chenab river catchment but also deteriorate the downstream water resources. In this study, potential soil erosion (PSE) is estimated from the transboundary Chenab river catchment using the Revised Universal Soil Loss Equation (RUSLE), coupled with remote sensing (RS) and geographic information system (GIS). Land Use of the European Space Agency (ESA), Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) data, and world soil map of Food and Agriculture Organization (FAO)/The United Nations Educational, Scientific and Cultural Organization were incorporated into the study. The SY was estimated on monthly, quarterly, seasonal, and annual time-scales using sediment delivery ratio (SDR) estimated through the area, slope, and curve number (CN)-based approaches. The 30-year average PSE from the Chenab river catchment was estimated as 177.8, 61.5, 310.3, 39.5, 26.9, 47.1, and 99.1 tons/ha for annual, rabi, kharif, fall, winter, spring, and summer time scales, respectively. The 30-year average annual SY from the Chenab river catchment was estimated as 4.086, 6.163, and 7.502 million tons based on area, slope, and CN approaches. The time series trends analysis of SY indicated an increase of 0.0895, 0.1387, and 0.1698 million tons per year for area, slope, and CN-based approaches, respectively. It is recommended that the areas, except for slight erosion intensity, should be focused on framing strategies for control and mitigation of soil erosion in the Chenab river catchment. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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19 pages, 2345 KiB

Open AccessFeature PaperArticle

Comparison of the Applicability of Different Soil Erosion Models to Predict Soil Erodibility Factor and Event Soil Losses on Loess Slopes in Hungary

by Boglárka Keller, Csaba Centeri, Judit Alexandra Szabó, Zoltán Szalai and Gergely Jakab

Water 2021, 13(24), 3517; https://doi.org/10.3390/w13243517 - 09 Dec 2021

Cited by 7 | Viewed by 2810

Abstract

Climate change induces more extreme precipitation events, which increase the amount of soil loss. There are continuous requests from the decision-makers in the European Union to provide data on soil loss; the question is, which ones should we use? The paper presents the [...] Read more.

Climate change induces more extreme precipitation events, which increase the amount of soil loss. There are continuous requests from the decision-makers in the European Union to provide data on soil loss; the question is, which ones should we use? The paper presents the results of USLE (Universal Soil Loss Equation), RUSLE (Revised USLE), USLE-M (USLE-Modified) and EPIC (Erosion-Productivity Impact Calculator) modelling, based on rainfall simulations performed in the Koppány Valley, Hungary. Soil losses were measured during low-, moderate- and high-intensity rainfalls on cultivated soils formed on loess. The soil erodibility values were calculated by the equations of the applied soil erosion models and ranged from 0.0028 to 0.0087 t ha h ha⁻¹ MJ⁻¹ mm⁻¹ for the USLE-related models. EPIC produced larger values. The coefficient of determination resulted in an acceptable correlation between the measured and calculated values only in the case of USLE-M. Based on other statistical indicators (e.g., NSEI, RMSE, PBIAS and relative error), RUSLE, USLE and USLE-M resulted in the best performance. Overall, regardless of being non-physically based models, USLE-type models seem to produce accurate soil erodibility values, thus modelling outputs. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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17 pages, 3384 KiB

Open AccessFeature PaperArticle

Models of Gully Erosion by Water

by Aleksey Sidorchuk

Water 2021, 13(22), 3293; https://doi.org/10.3390/w13223293 - 21 Nov 2021

Cited by 7 | Viewed by 2738

Abstract

The type of modelling of gully erosion for the projects of land management depend on the targets and degree of details of these projects, as well as on the availability of input data. The set of four models cover a broad range of [...] Read more.

The type of modelling of gully erosion for the projects of land management depend on the targets and degree of details of these projects, as well as on the availability of input data. The set of four models cover a broad range of possible applications. The most detailed information about predicted gullies, change of their depth, width, and volume throughout the gully lifetime is obtained with the gully erosion and thermoerosion dynamic model. The calculation requires the time series of surface runoff, catchment relief, and lithology and the complex of coefficients and parameters, some of which can be estimated only by model calibration on the measurements. The difficulty in obtaining some of these coefficients makes it necessary to use less complicated models. The stable gully model predicts final gully depths and widths and is useful for projects where only stable gully geometry is used. The modified area–slope approach is used in the two simplest models, where the position on the slopes of possible gullies is calculated without details of the gully geometry. One of these models calculates total erosion potential, taking into account all water runoff transforming a gully. The second calculates gully erosion risk, using the information about slope inclination, contributing area and maximum surface runoff. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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16 pages, 9151 KiB

Open AccessArticle

Structural Connectivity of Sediment Affected by Check Dams in Loess Hilly-Gully Region, China

by Leichao Bai, Juying Jiao, Nan Wang and Yulan Chen

Water 2021, 13(19), 2644; https://doi.org/10.3390/w13192644 - 25 Sep 2021

Cited by 7 | Viewed by 1852

Abstract

Check dams play an irreplaceable role in soil and water conservation in the Chinese Loess Plateau region. However, there are few analyses on the connection between check dams and the downstream channel and the impact on structural connectivity and sediment interception efficiency. Based [...] Read more.

Check dams play an irreplaceable role in soil and water conservation in the Chinese Loess Plateau region. However, there are few analyses on the connection between check dams and the downstream channel and the impact on structural connectivity and sediment interception efficiency. Based on a field survey, this study classified the connection mode between check dams and the downstream channel, and the actual control area percentage by discharge canal in dam land was used to quantitatively evaluate the degree of the structural connectivity of sediment between the check dam and the downstream channel. The analysis results show that the connection mode can be divided into eleven categories with different structural connectivity. The different connection modes and its combination mode of check dams and downstream channels in dam systems have a large difference, and the structural connectivity of the dam system is less than or equal to that of the sum of single check dams in a watershed. The degree of structural connectivity of a dam system will be greatly reduced if there is a main control check dam with no discharge canal in the lower reaches of the watershed. Compared with a single check dam, the structural connectivity of a dam system is reduced by 0–42.38%, with an average of 11.18%. According to the difference in connection mode and structural connectivity of check dams and dam systems in the four typical small watersheds, the optimization methods for connection mode in series, parallel and hybrid dam systems were proposed. The research results can provide a reference for the impact of a check dam on the sediment connectivity and the sediment interception efficiency in a watershed and can also guide the layout of a dam system and the arrangement of drainage facilities. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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24 pages, 7503 KiB

Open AccessArticle

Sediment Influx and Its Drivers in Farmers’ Managed Irrigation Schemes in Ethiopia

by Zerihun Anbesa Gurmu, Henk Ritzema, Charlotte de Fraiture, Michel Riksen and Mekonen Ayana

Water 2021, 13(13), 1747; https://doi.org/10.3390/w13131747 - 24 Jun 2021

Cited by 5 | Viewed by 2540

Abstract

Excessive soil erosion hampers the functioning of many irrigation schemes throughout sub-Saharan Africa, increasing management difficulties and operation and maintenance costs. River water is often considered the main source of sedimentation, while overland sediment inflow is overlooked. From 2016 to 2018, participatory research [...] Read more.

Excessive soil erosion hampers the functioning of many irrigation schemes throughout sub-Saharan Africa, increasing management difficulties and operation and maintenance costs. River water is often considered the main source of sedimentation, while overland sediment inflow is overlooked. From 2016 to 2018, participatory research was conducted to assess sediment influx in two irrigation schemes in Ethiopia. Sediment influx was simulated using the revised universal soil loss equation (RUSLE) and compared to the amount of sediment removed during desilting campaigns. The sediment deposition rate was 308 m³/km and 1087 m³/km, respectively, for the Arata-Chufa and Ketar schemes. Spatial soil losses amounts to up to 18 t/ha/yr for the Arata-Chufa scheme and 41 t/ha/yr for the Ketar scheme. Overland sediment inflow contribution was significantly high in the Ketar scheme accounting for 77% of the deposited sediment, while only 4% of the sedimentation at the Arata-Chufa scheme came from overland flow. Feeder canal length and the absence of canal banks increased the sedimentation rate, however, this was overlooked by the stakeholders. We conclude that overland sediment inflow is an often neglected component of canal sedimentation, and this is a major cause of excessive sedimentation and management problems in numerous irrigation schemes in sub-Saharan Africa. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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11 pages, 1450 KiB

Open AccessArticle

Effects of Infiltration Amounts on Preferential Flow Characteristics and Solute Transport in the Protection Forest Soil of Southwestern China

by Mingfeng Li, Jingjing Yao, Ru Yan and Jinhua Cheng

Water 2021, 13(9), 1301; https://doi.org/10.3390/w13091301 - 06 May 2021

Cited by 15 | Viewed by 2551

Abstract

Preferential flow has an important role as it strongly influences solute transport in forest soil. The quick passage of water and solutes through preferential flow paths without soil absorption results in considerable water loss and groundwater pollution. However, preferential flow and solute transport [...] Read more.

Preferential flow has an important role as it strongly influences solute transport in forest soil. The quick passage of water and solutes through preferential flow paths without soil absorption results in considerable water loss and groundwater pollution. However, preferential flow and solute transport under different infiltration volumes in southwestern China remain unclear. Three plots, named P20, P40 and P60, were subjected to precipitation amounts of 20, 40 and 60 mm, respectively, to investigate preferential flow and solute transport characteristics via field multiple-tracer experiments. Stained soils were collected to measure Br⁻ and NO₃⁻ concentrations. This study demonstrated that precipitation could promote dye tracer infiltration into deep soils. The dye tracer reached the maximum depth of 40 cm in P60. Dye coverage generally reduced with greater depth, and sharp reductions were observed at the boundary of matrix flow and preferential flow. Dye coverage peaked at the soil depth of 15 cm in P40. This result demonstrated that lateral infiltration was enhanced. The long and narrow dye coverage pattern observed in P60 indicated the occurrence of macropore flow. Br⁻ and NO₃⁻ were found at each soil depth where preferential flow had moved. Increasing precipitation amounts increased Br⁻ and NO₃⁻ concentration and promoted solute movement into deep soil layers. Solute concentration peaked at near the end of the preferential flow path and when preferential flow underwent lateral movement. These results indicated that the infiltration volume and transport capacity of preferential flow had important effects on the distribution of Br⁻ and NO₃⁻ concentrations. The results of this study could help expand our understanding of the effects of preferential flow on solute transport and provide some suggestions for protection forest management in southwestern China. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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19 pages, 63400 KiB

Open AccessArticle

Controlling Factors of Badland Morphological Changes in the Emilia Apennines (Northern Italy)

by Paola Coratza and Carlotta Parenti

Water 2021, 13(4), 539; https://doi.org/10.3390/w13040539 - 19 Feb 2021

Cited by 9 | Viewed by 2950

Abstract

Badlands are typical erosional landforms of the Apennines (Northern Italy) that form on Plio-Pleistocene clayey bedrock and rapidly evolve. The present study aimed at identification and assessment of the areal and temporal changes of badlands within a pilot area of the Modena Province [...] Read more.

Badlands are typical erosional landforms of the Apennines (Northern Italy) that form on Plio-Pleistocene clayey bedrock and rapidly evolve. The present study aimed at identification and assessment of the areal and temporal changes of badlands within a pilot area of the Modena Province (Emilia Apennines), where no previous detailed investigation has been carried out. For this purpose, a diachronic investigation was carried out to map the drainage basin and the drainage networks of the linear erosion features in the study area during the last 40 years, and to evaluate changes in badlands drainage basins morphometry and surface, land use and pluviometry. The investigation carried out indicated a general stabilisation trend of the badlands in the study area. In fact, a reduction in the bare surface area from 6187.1 m² in 1973 to 4214.1 m² in 2014 (31%), due to an intensified revegetation process around the badland areas, has been recorded. This trend, in line with the results of research carried out in other sector of the Northern Apennines, is mainly due to intensive land use changes, mostly the increase in forest cover and the reduction of agricultural land, that occurred in the study area from the 1970s onwards. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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15 pages, 27861 KiB

Open AccessEditor’s ChoiceArticle

Effect of Freeze-Thaw Cycles on Soil Detachment Capacities of Three Loamy Soils on the Loess Plateau of China

by Jian Lu, Baoyang Sun, Feipeng Ren, Hao Li and Xiyun Jiao

Water 2021, 13(3), 342; https://doi.org/10.3390/w13030342 - 29 Jan 2021

Cited by 13 | Viewed by 2352

Abstract

Soil detachment is the initial phase of soil erosion and is of great significance to study in seasonal freeze-thaw regions. In order to elucidate the effects mechanism of freeze-thaw cycles on soil detachment capacity of different soils, a sandy loam, a silt loam, [...] Read more.

Soil detachment is the initial phase of soil erosion and is of great significance to study in seasonal freeze-thaw regions. In order to elucidate the effects mechanism of freeze-thaw cycles on soil detachment capacity of different soils, a sandy loam, a silt loam, and a clay loam were subjected to 0, 1, 5, 10, 15, and 20 freeze-thaw cycles before they were scoured. The results revealed that with increased freeze-thaw cycles, soil bulk density and water-stable aggregates content decreased after the first few times and then kept nearly stable after about 10 cycles, especially for sandy loam. The shear strength of all soils gradually decreased as freeze-thaw cycles increased, except the values of clay loam increased subsequent to the 5th and 15th cycles. After the 20th cycle, the degree of decline of silt loam was the greatest (77.72%), followed by sandy loam (63.18%) and clay loam (39.77%). The soil organic matter of clay loam was much greater than silt loam and sandy loam and all significantly increased after freeze-thaw. Soil detachment capacity of silt loam and sandy loam was positively correlated with freeze-thaw cycle, which was contrary to findings for clay loam. The values of clay loam increased at first and then decreased during the cycles, reaching minimum values at about the 15–20th cycle. After the 20th cycle, the values of sandy loam and silt loam significantly increased 1.62 and 4.74 times over unfrozen, respectively, which was greater than clay loam (0.53 times). A nonlinear regression analysis indicated that the soil detachment capacity of silt loam could be estimated well by soil properties (R² = 0.87, p < 0.05). This study can provide references for the study of the soil erosion mechanism in seasonal freeze-thaw regions. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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35 pages, 27390 KiB

Open AccessArticle

Impact of Land Cover Change Due to Armed Conflicts on Soil Erosion in the Basin of the Northern Al-Kabeer River in Syria Using the RUSLE Model

by Hussein Almohamad

Water 2020, 12(12), 3323; https://doi.org/10.3390/w12123323 - 26 Nov 2020

Cited by 18 | Viewed by 4196

Abstract

Due to armed conflicts, the sudden changes in land cover are among the most drastic and recurring shocks on an international scale, and thus, have become a major source of threat to soil and water conservation. Throughout this analysis, the impact of land [...] Read more.

Due to armed conflicts, the sudden changes in land cover are among the most drastic and recurring shocks on an international scale, and thus, have become a major source of threat to soil and water conservation. Throughout this analysis, the impact of land cover change on spatio-temporal variations of soil erosion from 2009/2010 to 2018/2019 was investigated using the Revised Universal Soil Loss Equation (RUSLE) model. The goal was to identify the characteristics and variations of soil erosion under armed conflicts in the basin of the Northern Al-Kabeer river in Syria. The soil erosion rate is 4 t ha⁻¹ year⁻¹ with a standard deviation of 6.4 t ha⁻¹ year⁻¹. In addition, the spatial distribution of erosion classes was estimated. Only about 10.1% of the basin is subject to a tolerable soil erosion rate and 79.9% of the study area experienced erosion at different levels. The soil erosion area of regions with no changes was 10%. The results revealed an increase in soil erosion until 2013/2014 and a decrease during the period from 20013/2014 to 2018/2019. This increase is a result of forest fires under armed conflict, particularly toward the steeper slopes. Coniferous forest as well as transitional woodland and scrub are the dominant land cover types in the upper part of the basin, for which the average post-fire soil loss rates (caused by factor C) were 200% to 800% higher than in the pre-fire situation. In the period from 2013/2014 to 2019/2020, soil erosion was mitigated due to a ceasefire that was agreed upon after 2016, resulting in decreased human pressures on soils in contested areas. By comparing 2009/2010 (before war) with 2018/2019 (at the end of the war stage), it can be concluded that the change in C factors slowed down the deterioration trend of soil erosion and reduced the average soil erosion rate in more than half of the basin by about 10–75%. The area concerned is located in the western part of the basin and is relatively far from the centers of armed conflicts. In contrast, the areas with increased soil erosion by about 60–400% are situated in the northeast and east, with shorter distances to armed conflict centers. These findings can be explained by forest fires, after which the burned forests were turned into agricultural land or refugee camps and road areas. Understanding the complex biophysical and socio-economic interactions of exposure to land loss is a key to guarantee regional environmental protection and to conserve the ecological quality of soil and forest systems. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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17 pages, 2928 KiB

Open AccessEditor’s ChoiceArticle

The Use of Various Rainfall Simulators in the Determination of the Driving Forces of Changes in Sediment Concentration and Clay Enrichment

by Judit Alexandra Szabó, Csaba Centeri, Boglárka Keller, István Gábor Hatvani, Zoltán Szalai, Endre Dobos and Gergely Jakab

Water 2020, 12(10), 2856; https://doi.org/10.3390/w12102856 - 14 Oct 2020

Cited by 7 | Viewed by 2510

Abstract

Soil erosion is a complex, destructive process that endangers food security in many parts of the world; thus, its investigation is a key issue. While the measurement of interrill erosion is a necessity, the methods used to carry it out vary greatly, and [...] Read more.

Soil erosion is a complex, destructive process that endangers food security in many parts of the world; thus, its investigation is a key issue. While the measurement of interrill erosion is a necessity, the methods used to carry it out vary greatly, and the comparison of the results is often difficult. The present study aimed to examine the results of two rainfall simulators, testing their sensitivity to different environmental conditions. Plot-scale nozzle type rainfall simulation experiments were conducted on the same regosol under both field and laboratory conditions to compare the dominant driving factors of runoff and soil loss. In the course of the experiments, high-intensity rainfall, various slope gradients, and different soil surface states (moisture content, roughness, and crust state) were chosen as the response parameters, and their driving factors were sought. In terms of the overall erosion process, the runoff, and soil loss properties, we found an agreement between the simulators. However, in the field (a 6 m² plot), the sediment concentration was related to the soil conditions and therefore its hydrological properties, whereas in the laboratory (a 0.5 m² plot), slope steepness and rainfall intensity were the main driving factors. This, in turn, indicates that the design of a rainfall simulator may affect the results of the research it is intended for, even if the differences occasioned by various designs may be of a low order. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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17 pages, 5564 KiB

Open AccessArticle

Slope Erosion and Hydraulics during Thawing of the Sand-Covered Loess Plateau

by Yuanyi Su, Peng Li, Zongping Ren, Lie Xiao, Tian Wang and Yi Zhang

Water 2020, 12(9), 2461; https://doi.org/10.3390/w12092461 - 01 Sep 2020

Cited by 8 | Viewed by 2092

Abstract

Seasonal freeze-thaw processes have led to severe soil erosion globally. Slopes are particularly susceptible to changes in runoff, it can be useful to study soil erosion mechanisms. We conducted meltwater flow laboratory experiments to quantify the temporal and spatial distribution of hydraulic parameters [...] Read more.

Seasonal freeze-thaw processes have led to severe soil erosion globally. Slopes are particularly susceptible to changes in runoff, it can be useful to study soil erosion mechanisms. We conducted meltwater flow laboratory experiments to quantify the temporal and spatial distribution of hydraulic parameters on sandy slopes in relation to runoff and sediment yield under constant flow, different soil conditions (unfrozen slope: US; frozen slope: FS), and variable sand thickness. The results showed that sand can prolong initial runoff time, and US and FS have significantly different initial runoff times. There was a significant linear relationship between the cumulative runoff and the cumulative sediment yield. Additionally, hydrodynamic parameters of US and FS varied with time and spatially, as the distance between US and FS is linearly related to the top of the slope. We found that the main runoff flow pattern was composed of laminar flow and supercritical flow. There was a significant linear relationship between flow velocity and hydraulic parameters. The flow velocity is the best hydraulic parameter to simulate the trend of slope erosion process. This study can provide a scientific basis for a model of slope erosion during thawing for the Loess Plateau. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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14 pages, 1726 KiB

Open AccessArticle

Can Lumped Characteristics of a Contributing Area Provide Risk Definition of Sediment Flux?

by Barbora Jáchymová, Josef Krása, Tomáš Dostál and Miroslav Bauer

Water 2020, 12(6), 1787; https://doi.org/10.3390/w12061787 - 23 Jun 2020

Cited by 5 | Viewed by 1795

Abstract

Accelerated soil erosion by water has many offsite impacts on the municipal infrastructure. This paper discusses how to easily detect potential risk points around municipalities by simple spatial analysis using GIS. In the Czech Republic, the WaTEM/SEDEM model is verified and used in [...] Read more.

Accelerated soil erosion by water has many offsite impacts on the municipal infrastructure. This paper discusses how to easily detect potential risk points around municipalities by simple spatial analysis using GIS. In the Czech Republic, the WaTEM/SEDEM model is verified and used in large scale studies to assess sediment transports. Instead of computing actual sediment transports in river systems, WaTEM/SEDEM has been innovatively used in high spatial detail to define indices of sediment flux from small contributing areas. Such an approach has allowed for the modeling of sediment fluxes in contributing areas with above 127,484 risk points, covering the entire Czech Republic territory. Risk points are defined as outlets of contributing areas larger than 1 ha, wherein the surface runoff goes into residential areas or vulnerable bodies of water. Sediment flux indices were calibrated by conducting terrain surveys in 4 large watersheds and splitting the risk points into 5 groups defined by the intensity of sediment transport threat. The best sediment flux index resulted from the correlation between the modeled total sediment input in a 100 m buffer zone of the risk point and the field survey data (R² from 0.57 to 0.91 for the calibration watersheds). Correlation analysis and principal component analysis (PCA) of the modeled indices and their relation to 11 lumped characteristics of the contributing areas were computed (average K-factor; average R-factor; average slope; area of arable land; area of forest; area of grassland; total watershed area; average planar curvature; average profile curvature; specific width; stream power index). The comparison showed that for risk definition the most important is a combination of morphometric characteristics (specific width and stream power index), followed by watershed area, proportion of grassland, soil erodibility, and rain erosivity (described by PC2). Full article

(This article belongs to the Special Issue Soil Water Erosion)

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19 pages, 4218 KiB

Open AccessArticle

Comparing Rainfall Erosivity Estimation Methods Using Weather Radar Data for the State of Hesse (Germany)

by Jennifer Kreklow, Bastian Steinhoff-Knopp, Klaus Friedrich and Björn Tetzlaff

Water 2020, 12(5), 1424; https://doi.org/10.3390/w12051424 - 16 May 2020

Cited by 12 | Viewed by 2994

Abstract

Rainfall erosivity exhibits a high spatiotemporal variability. Rain gauges are not capable of detecting small-scale erosive rainfall events comprehensively. Nonetheless, many operational instruments for assessing soil erosion risk, such as the erosion atlas used in the state of Hesse in Germany, are still [...] Read more.

Rainfall erosivity exhibits a high spatiotemporal variability. Rain gauges are not capable of detecting small-scale erosive rainfall events comprehensively. Nonetheless, many operational instruments for assessing soil erosion risk, such as the erosion atlas used in the state of Hesse in Germany, are still based on spatially interpolated rain gauge data and regression equations derived in the 1980s to estimate rainfall erosivity. Radar-based quantitative precipitation estimates with high spatiotemporal resolution are capable of mapping erosive rainfall comprehensively. In this study, radar climatology data with a spatiotemporal resolution of 1 km² and 5 min are used alongside rain gauge data to compare erosivity estimation methods used in erosion control practice. The aim is to assess the impacts of methodology, climate change and input data resolution, quality and spatial extent on the R-factor of the Universal Soil Loss Equation (USLE). Our results clearly show that R-factors have increased significantly due to climate change and that current R-factor maps need to be updated by using more recent and spatially distributed rainfall data. Radar climatology data show a high potential to improve rainfall erosivity estimations, but uncertainties regarding data quality and a need for further research on data correction approaches are becoming evident. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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26 pages, 10352 KiB

Open AccessArticle

Gully Head-Cut Distribution Modeling Using Machine Learning Methods—A Case Study of N.W. Iran

by Alireza Arabameri, Wei Chen, Thomas Blaschke, John P. Tiefenbacher, Biswajeet Pradhan and Dieu Tien Bui

Water 2020, 12(1), 16; https://doi.org/10.3390/w12010016 - 19 Dec 2019

Cited by 26 | Viewed by 4350

Abstract

To more effectively prevent and manage the scourge of gully erosion in arid and semi-arid regions, we present a novel-ensemble intelligence approach—bagging-based alternating decision-tree classifier (bagging-ADTree)—and use it to model a landscape’s susceptibility to gully erosion based on 18 gully-erosion conditioning factors. The [...] Read more.

To more effectively prevent and manage the scourge of gully erosion in arid and semi-arid regions, we present a novel-ensemble intelligence approach—bagging-based alternating decision-tree classifier (bagging-ADTree)—and use it to model a landscape’s susceptibility to gully erosion based on 18 gully-erosion conditioning factors. The model’s goodness-of-fit and prediction performance are compared to three other machine learning algorithms (single alternating decision tree, rotational-forest-based alternating decision tree (RF-ADTree), and benchmark logistic regression). To achieve this, a gully-erosion inventory was created for the study area, the Chah Mousi watershed, Iran by combining archival records containing reports of gully erosion, remotely sensed data from Google Earth, and geolocated sites of gully head-cuts gathered in a field survey. A total of 119 gully head-cuts were identified and mapped. To train the models’ analysis and prediction capabilities, 83 head-cuts (70% of the total) and the corresponding measures of the conditioning factors were input into each model. The results from the models were validated using the data pertaining to the remaining 36 gully locations (30%). Next, the frequency ratio is used to identify which conditioning-factor classes have the strongest correlation with gully erosion. Using random-forest modeling, the relative importance of each of the conditioning factors was determined. Based on the random-forest results, the top eight factors in this study area are distance-to-road, drainage density, distance-to-stream, LU/LC, annual precipitation, topographic wetness index, NDVI, and elevation. Finally, based on goodness-of-fit and AUROC of the success rate curve (SRC) and prediction rate curve (PRC), the results indicate that the bagging-ADTree ensemble model had the best performance, with SRC (0.964) and PRC (0.978). RF-ADTree (SRC = 0.952 and PRC = 0.971), ADTree (SRC = 0.926 and PRC = 0.965), and LR (SRC = 0.867 and PRC = 0.870) were the subsequent best performers. The results also indicate that bagging and RF, as meta-classifiers, improved the performance of the ADTree model as a base classifier. The bagging-ADTree model’s results indicate that 24.28% of the study area is classified as having high and very high susceptibility to gully erosion. The new ensemble model accurately identified the areas that are susceptible to gully erosion based on the past patterns of formation, but it also provides highly accurate predictions of future gully development. The novel ensemble method introduced in this research is recommended for use to evaluate the patterns of gullying in arid and semi-arid environments and can effectively identify the most salient conditioning factors that promote the development and expansion of gullies in erosion-susceptible environments. Full article

(This article belongs to the Special Issue Soil Water Erosion)

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