Soil Erosion Processes Research Articles

Quantifying the importance of different erosion processes and soil and water conservation measure collapses following an extreme rainstorm in the Chinese Loess Plateau

AbstractExtreme rainfall events can make disproportionally larger contributions than common rainfalls to soil erosion rates. Yet assessing the importance of different soil erosion processes during such events remains a critical challenge, especially due to a lack of field observations. Based on detailed field surveys and remote‐sensing analyses, we therefore provide erosion budgets for three representative catchments in the Chinese Loess Plateau, following an exceptional rainstorm event (July 26, 2017; estimated return period: 200 years). Our results show that the associated catchment‐scale erosion intensities were 2815 ± 529 t km‐2 for rill erosion, 787 ± 486 t km‐2 for gully erosion, 4433 ± 657 t km‐2 for landsliding and 3927 ± 1009 t km‐2 for the collapse of implemented soil and water conservation measures (SWCMs, specifically terraces and check‐dams). Hence, landslides (37 ± 4%) and SWCMs collapses (33 ± 4%) were the most important sediment sources, followed by rill (24 ± 3%) and gully erosion (7 ± 4%). The lower contribution of gully erosion likely results from earlier vegetation restoration efforts. Overall, our results indicate that successful erosion control during extreme events strongly depends on integrative and robust catchment management strategies. Specifically, the spatial intersecting of forestland and grassland can play a large role, with reforestation on problematic slopes being an important strategy limiting rill and gully erosion. Sufficient consideration should be given to the planning and maintenance of terraces and check‐dams. The latter should be constructed with good flood‐release facilities, meanwhile many small‐scale dams likely work better than a few large ones. Likewise, (unpaved) roads should receive attention as they can also be a significant runoff and sediment source.

Evaluation of factors of origin and intensity of erosion processes in Novosilskaya agro-forest reclaim station

The materials of scientific research provide information about the processes of the origin of ravines on sloping lands. During the snowmelt period, water flows from the plowed fields into the hydrographic network. There are washouts, which cause the erosion processes. The level of soil erosion during snowmelt increases in direct proportion to the length of the slope. There are two sets of factors that have a decisive influence on the formation of erosion processes – natural and anthropogenic. Degradation processes usually appear when the factors of these two complexes are combined. According to the long-term experimental data of the Novosilskaya agro-forest reclaim station, the increase in coastal erosion in length is 1.6 m, and bottom erosion is 2.1 m (on average per year). To protect agricultural landscapes from negative processes of soil erosion, the anti-erosion measures should be applied.

137Cs-based analysis of soil redistribution in the Integrated Watershed Management intervention area in northern Ethiopia

Spatial patterns of trace isotope cesium-137 (137Cs) can be strongly correlated with soil movement in a landscape, thereby allowing assessments of soil erosion and deposition processes, based on these patterns. Our study assessed how soil organic carbon (SOC) stocks were related to the redistribution of 137Cs in prevalent forest and agricultural land-use systems in a north Ethiopian watershed undergoing land rehabilitation. Composite soil samples were collected from 0 to 5, 5–10, 10–20, and 20–30 cm layers of exclosures, croplands, rangelands, and bare lands at different slope positions. Reference samples were collected from a vegetated hilltop with no anthropogenic soil disturbance history. The use of 137Cs analysis was not effective in revealing SOC dynamics in croplands, which was probably a result of soil tillage and generally low SOC contents. Otherwise, 137Cs tracing was a suitable method for the soil redistribution assessment in the tropical environment, owing to sufficient amount of the isotope detected following the original fallout. Comparisons of 137Cs contents between the reference and sampling sites revealed a gap in 137Cs inventories in 87% of all locations, thereby indicating severe erosion, especially on the backslopes. Some of the examined samples, mostly from rangelands and exclosures, exhibited 137Cs activities that were higher than the reference, signifying these sites as depositional areas for soil material eroded elsewhere. Soil movements indicated by 137Cs profiles, were particularly substantial in rangelands, where 137Cs stock varied significantly according to the slope positions and soil depths. Notably, significant correlations between SOC stocks and 137Cs levels in exclosures suggested that both the prevention of soil loss and the capture of soil eroded from degraded sites fortified SOC accumulation. This suggests that not only the increase in vegetation cover but also the soil deposition was an attribute of the land rehabilitation process.

Temporal and spatial variability of suspended sediment rating curves for rivers draining into the Ethiopian Rift Valley

AbstractQuantification of suspended sediment dynamics is a proxy for the intensity of soil erosion processes in a catchment. However, direct measurement of suspended sediments is difficult. Long‐term‐based discharge‐suspended sediment relationships often fail to provide sufficiently accurate results due to the temporal variations in sediment supply. This study evaluates temporal variations in suspended sediment‐discharge relations for six stations in two selected catchments within the Gamo Highlands in the southern Ethiopian Rift Valley. During a three‐year period (2018–2020), discharge was monitored at a 10‐min interval using a TD‐diver, while 1938 samples of suspended sediment concentration were taken at specific events. Observed suspended sediment concentration varied between 0.04 and 130 kg m−3 for discharge ranging between quasi‐zeros to 339 m3 s−1. The results show that pooled annual datasets lead to unsatisfying sediment rating curves and large errors in estimated sediment load. However, stratification of the data into three rainy season periods strongly improved the performance of the sediment rating curves. The development of a vegetative cover throughout the rainy season largely controls sediment supply from hillslopes to the river channel and hence the shape of the sediment rating curves. Furthermore, localized bank erosion and gully head dynamics also lead to important interannual changes in sediment rating curves within one river system, as well as between different rivers. Thus, attention should be given to possible errors due to high temporal and spatial variability while using discharge‐suspended sediment relations to quantify sediment load.

Pre/Post-Fire Soil Erosion and Evaluation of Check-Dams Effectiveness in Mediterranean Suburban Catchments Based on Field Measurements and Modeling

The present study was conducted in the suburban forest of Thessaloniki city (Seich Sou), which constitutes one of the most significant suburban forests in Greece. In 1997, more than the half of the forest area was destroyed by a wildfire, after which soil erosion and flood control works (check-dams) were constructed in the burned areas. The aim of the study is to estimate the annual soil erosion rate for the last 30 years (pre- and post-fire periods) applying the WaTEM/SEDEM model, in order to investigate the impact of this wildfire on soil erosion, the effectiveness of the flood- and erosion-control works and the level of forest regeneration. It is the first time that WaTEM/SEDEM was calibrated and validated in Greece, taking into account soil erosion records from the 18 check-dams that were constructed in the study area in 2001. The mean annual erosion rate was 0.0419 t/ha/year, 0.998 t/ha/year and 0.08 t/ha/year for the pre-fire period, the first 3 years and 20 years after the fire, respectively. The results showed a very low erosion rate for the pre-fire period, an expected significant increase 3 years after the wildfire and a gradual decrease in the subsequent years until 2021. However, it seems that the post-fire regeneration of the forest has not been fully achieved, since the annual soil erosion rate at the long-term post-fire period is double compared with the pre-fire period. Concerning the check-dams’ effectiveness, it was observed that after 20 years of operation, they were non-silted, and most of them retained a small amount of sediments. This fact could be attributed to multiple factors such as the very thin soil depth, fire severity and catchment geomorphology, though the main reason seems to be the time elapsed between fire occurrence and the check-dams’ construction. The results of this study advance/strengthen the knowledge concerning the pre/post-fire soil erosion processes in already degraded ecosystems, while the calibrated model could serve as a useful tool able to be applied in other Mediterranean catchments of similar characteristics.

The impact of land use landscape pattern on river hydrochemistry at multi-scale in an inland river basin, China

• The rainy season was the key period when land use landscape pattern affected the river water chemistry. • The sub-watershed scale was the core scale that affects river water chemistry as a whole. • The “source-sink” functions of the same land use type changes with the change of scale. • Forestland and grassland have obvious interception effect on soil erosion at riparian scale. The impact of the land use landscape pattern on river hydrochemistry has significant scale effects. It is the premise and foundation of landscape optimization and the conservation of water resources to accurately identify the core scale of the landscape pattern impacting on river hydrochemistry. Taking Binggou River Basin in the source region of Shiyang River Basin as the study area, this paper selected the three spatial scales of catchment area, buffer zone, and riparian zone, and the relationships between land use types and landscape indices and river hydrochemical characteristics were analyzed at different spatio-temporal scales using redundancy analysis. The results showed that the hydrochemistry characteristics of Binggou River Basin had strong temporal variability, and the rainy season was the key period when the land use landscape pattern affected the river hydrochemistry. The sub-watershed and riparian scales were the core scales of influence of the landscape pattern on river hydrochemistry in Binggou River Basin. In particular, the landscape pattern index contributed the most to the river hydrochemistry at the sub-watershed scale on the whole, which was the core scale affecting river hydrochemistry. The “source” or “sink” functions of the same land use type also changed as the scale changed. Forest land showed weak “source” effect at the sub-watered scale, but a strong interception effect on the soil erosion process at the riparian scale, which is a typical “sink” landscape.

Impacts of grass planting density and components on overland flow hydraulics and soil loss

AbstractAlthough abundant studies have confirmed the positive effect of vegetation on runoff and soil erosion reduction, few studies have clarified the effects of planting density and its components (aboveground parts and roots) on slope runoff and soil erosion mechanisms. A series of field experimental plots were constructed on two slopes (3°, 6°), including a bare land plot as the control, three grassed plots with three grass (Agropyron cristatum) planting densities of 20 cm × 20 cm, 15 cm × 15 cm, and 10 cm × 10 cm, and a plot without aboveground parts, to examine runoff and soil erosion process under simulated overland flow of 4, 8, 12, and 16 L min−1. The runoff regime was transformed from supercritical‐turbulent flow to subcritical‐laminar flow with increasing planting density. Grass significantly reduced the runoff rate (RR), velocity (V), shear stress (τ), stream power (ω), and soil loss rate (SLR), with average reductions of 38.6%, 56.6%, 76.5%, 87.6%, and 61.9%, respectively. The aboveground parts contributed 74.1% and 75.1% of the total reduction in RR and V, respectively, while the grass roots contributed to 84.9%, 89.7%, 84.9%, and 69.7% of the reductions in Reynolds number, τ, ω, and SLR, respectively. RR, V, τ, ω, and SLR were significantly affected by slope, inflow discharge, root density, and the ratio of grass stem area to plot area. The runoff–sediment relationship changed from positively exponential function to linear and power functions with the planting density increased. Grass significantly weakened the sensitivity of soil erosion by reducing soil erodibility and improving critical hydrodynamic triggering soil erosion. This study improved the understanding of grass controlling soil and water loss, and the plants with well‐developed roots and planting space of 10–15 cm are preferred to provide a scientific reference for revegetation strategy.

Responses of Infiltration Potential and Soil-Erosion Processes to Rainfall Patterns in Two Types of Slopes over the Eastern Region of the Tibetan Plateau

Responses of Infiltration Potential and Soil-Erosion Processes to Rainfall Patterns in Two Types of Slopes over the Eastern Region of the Tibetan Plateau

Influence of combined stem vegetation distribution and discretization on the hydraulic characteristics of overland flow

Vegetation has important functions of conserving water sources, reducing surface sediment transport, slowing down the process of soil erosion, purifying soil quality and filtering pollutants, and plays an important role in soil and water conservation and environmental protection governance. Accurate simulation of the slope runoff process is important in the research of hydrological models. Existing distributed hydrological models use a single factor, slope vegetation, to determine the vegetation distribution pattern between slope grid units; thus, the homogenization process does not consider the influence of slope vegetation on the hydraulic characteristics. To clarify the effects of the combination and discrete distribution of stem-type vegetation on the hydraulic characteristics of overland flow, this study conducted 768 sets of indoor flume tests through six combined distributions, six discrete distributions, four slopes, and 16 flow discharges. The results show that: 1) Under the experimental conditions, overland flow is located in the transition and turbulent flow regions, and the flow pattern is mutually restricted by the combined distribution of vegetation, discrete distribution of vegetation, and slope. 2) The Darcy–Weisbach resistance coefficient increases with the increase in the combined diameter and dispersion of vegetative stems, which verifies that the results of the study on complex and varied vegetation overland flows obtained via generalized simulations of homogeneous vegetation deviate from the physical reality of overland flow. 3) An increase in the thickness of the integrated vegetation stems and the increase in the degree of dispersion of vegetation both lead to an increase in the vegetation coverage density. The change in vegetation density initiates the change in the flow pattern and resistance of the overland flow. 4) The total resistance under the combined vegetation cover is divided into morphological resistance and particle resistance. The proportion of particle resistance is smaller than that of morphological resistance and decreases with an increase in flow. 5) The influence of stem diameter, Reynolds number, and slope of the combined vegetation was considered comprehensively, and a flow-resistance calculation model was established.

Effect of plot size and precipitation magnitudes on the activation of soil erosion processes using simulated rainfall experiments in vineyards

Soil erosion is recognized as a threat to humankind and to natural ecosystems when sustainable limits are exceeded. Several researchers have used various tools, such as rainfall simulators, to assess extreme rainfall events and non-sustainable soil management practices. However, combinations of two different devices of different sizes has not been tested before, especially in vineyards. The aim is to verify whether plot size, connectivity processes and rainfall distribution affect the activation of soil erosion. In this research on soils cultivated with vineyards in the Moravia Region in the south-eastern part of the Czech Republic, we have performed various rainfall simulation experiments with a small device (1 × 1 m) and with a large device (8 × 1 m). Our results show that the surface runoff was approximately 30% higher on the small plot than on the large plot. The large rainfall simulator produced sediment concentration that was up to 3 times higher, and soil loss that was up to 1.5 times higher, even when the surface runoff was 30%–50% lower for the large rainfall simulator. We therefore conclude that there is a clear influence of surface length and plot size on surface runoff, soil loss and sediment concentration activation. When planning their experiments, researchers need to consider that the type of device can have a drastic influence on the final results. Two devices subjected to the same rainfall intensity (60 mm h−1) can produce very different results, e.g., depending on plot size and kinetic energy. Our results can be effectively used to plan soil protection measures and to inform local authorities about areas prone to flooding and about loss of sediments.

Simulation of Holocene soil erosion and sediment deposition processes in the Yellow River basin during the Holocene

The Yellow River Basin is ideal for studying fluvial landscape evolution under climate change and human activities. Quantitative reconstruction of soil erosion, sediment transport, and delta deposition in the basin enhances understanding of the dynamic mechanisms of fluvial surface processes. This study reconstructs the spatial and temporal distribution of precipitation and vegetation cover based on geological profile records, paleoclimatic datasets, and historical documentation in the Yellow River basin during the Holocene. A landscape evolution model (Landlab) is introduced to simulate soil erosion and sediment deposition processes. Modeling results show that soil erosion intensity in the middle reaches of the Yellow River was weak during the early and middle Holocene. Since the late Holocene, soil erosion has increased due to vegetation degradation, as the climate became drier, but with more fluctuations. Since 2.0 ka (1 ka = 1,000 calibrated a B.P.), and especially since 1.0 ka, soil erosion in the middle reaches of the Yellow River increased rapidly due to strong human activity, with the intensity-six times higher than the average level before the late Holocene. Average sediment deposition thickness in the lower reach of the Yellow River (North China Plain) was about 2.4 m, and sediment volume was about 3.6 × 1011 m3. The deposition rate and soil erosion intensity showed synchronous changes during the Holocene. Since 2.0 ka, the sediment load and deposition rate have increased rapidly, to 6–10 times higher than in the early and middle Holocene. On this basis, the effects of climate change and human activities on the evolution of the fluvial landscape are discussed.

Assessment of soil erosion risk using an integrated approach of GIS and Analytic Hierarchy Process (AHP) in Erzurum, Turkiye

Assessing soil erosion hazards and mapping the spatial distribution of soil erosion have an essential role in sustainable forest management. In this study, the potential soil erosion risk was evaluated through the Analytical Hierarchy Process (AHP) and Geographic Information Systems (GIS) in the Oltu forest planning unit, Erzurum. Seven erosion-related criteria, including slope, bedrock type, relative relief, drainage density and frequency, rainfall, and land use/land cover (LULC) were used for the present assessment. According to the AHP analysis, the slope was the most influential factor (21%) followed by bedrock type (19%), land cover (17%), and relative relief (14%) in the soil erosion process. The soil erosion risk in the study area was strongly influenced by the LULC where 59.46% is bare land with high erosion risk and 12.07%, with the lowest risk, is in an area with any forest cover. The estimated soil erosion risk was classified into five different classes namely very low, low, moderate, high, and very high. The results showed that this study area is highly prone to soil erosion. The larger proportion of the area (39.16%) is exposed to high to very high erosion, mainly determined by forest cover and geomorphology. To analyze the accuracy of the soil erosion risk map, 40 points were selected randomly in this study area. In these points, predicted values were compared to the real values obtained by Google Earth-colored images. The area under the ROC curve (AUC) method was applied to validate the efficiency of the AHP which showed a satisfactory accuracy of 81.00%. Findings presented that including the more influencing factors with a slope instead of including only the slope contributes to a more accurate erosion risk map. This study highlighted that GIS-based multi-criteria decision-making is a valuable and practical tool for decision-makers and land managers in creating soil erosion susceptibility maps and determining high-priority areas that require conservation measures for sustainable land use management by reducing the economic and ecological impacts of soil loss. Also, this approach can be practically applied in other planning units.

Soil Erosion Processes and Geographical Differentiation in Shaanxi during 1980–2015

It is important to couple the analysis of the effects of topography, climate, vegetation, and human activities on soil erosion to understand the dynamic characteristics of soil erosion under environmental change. This study investigated the impacts of geographic unit difference on soil erosion in the Shaanxi Province in China through the model simulation (RUSLE) and quantitative analysis. The following results were achieved. First, the amplitudes of environmental change varied at different rates in the three regions over the past 35 years (1980–2015). The frequency of severe rainstorms, the main trigger for soil erosion, intensified most in the Loess Plateau compared to the Qinling Mountains and Guanzhong Plain and led to an increase in the number of geological disasters in that region. In addition, after the 1990s, vegetation improved most in the Loess Plateau, and socioeconomic activities related to urbanization, another important driver of soil erosion, increased the most in Guanzhong Plain. Second, improved vegetation cover was the most significant contributor to the reduction in soil erosion during the past 35 years, although intensified rainstorms and human activities enhanced the risks of soil erosion. Third, the comparative study revealed that different environmental parameters dominated soil erosion processes in the three regions.

Contribution of fine roots mechanical property of Poaceae grasses to soil erosion resistance on the Loess Plateau

Plant roots play a key role in soil erosion process, but less studies are focused on analyze the soil erosion resistance in terms of grassland roots mechanical properties. The objective of this study was to examine the root diameter, root density, root tensile strength and soil shear strength for five typical and widely distributed Poaceae grasses in semi-arid regions, thus determine the contribution of roots of artificial grassland to soil erosion resistance. Results showed that the roots of five grasslands were densely distributed in the surface soils (0–10 cm). Bromus inermis had the strongest roots that characterized by the highest average tensile strength (40.2 MPa) The shear strength significantly increased as the vertical stress increased from 50 kPa to 300 kPa, but the degree varied with grassland types. Shear strength was also linearly correlated with root density when vertical pressure reached 300 kPa (p < 0.01, R2 = 0.47), indicating that high root density might help resist extreme external stress. Moreover, Bromus inermis showed a high soil cohesion of 122.7 kPa (next to the highest value of 128.71 kPa in Panicum virgatum). Overall, Bromus inermis showed the highest soil erosion resistance among these five grasslands, could be a good candidate in Poaceae artificial grasslands to improve soil shear strength for topsoil conservation. These findings have potential implications for understanding the contribution of Poaceae grasses’ roots on the topsoil reinforcement, and provide a theoretical basis for artificial grassland establishment on soil erosion resistance on the Loess Plateau.

Effects of raindrop temperature on the contributions of slaking and mechanical striking to aggregate disintegration during splash erosion

The influence of raindrop temperature on the soil erosion process has been reported. However, the role of raindrop temperature in aggregate disintegration is unclear. The aims of this study are to investigate the effects of raindrop temperatures on soil aggregate disintegration and to evaluate their effects on the contribution of slaking and mechanical striking to splash erosion. Deionized water and ethanol (95%) were employed as raindrop materials to quantify the effects of raindrop temperature on the contributions of slaking and mechanical striking to splash erosion. Raindrop temperatures were set to 2 °C, 10 °C and 20 °C, and the rainfall heights were set to 0.5 m, 1.0 m and 1.5 m. The results showed that the splash erosion rate decreased with increasing temperature in the Loam1 and Loamy sandy. The breakdown rate decreased with increasing temperature in ethanol tests. The influence of temperature on slaking was greater than that on mechanical striking. The contribution rates of mechanical striking and slaking decreased and increased with increasing temperature, respectively. Slaking contributed more to aggregate disintegration at 10 °C and 20 °C, while mechanical striking was the primary contributor at 2 °C in the Loam2 and Loamy sandy. The results provided a deeper understanding of the mechanism of splash erosion and contributed to improving soil erosion prediction models.

Effects of grass density on the runoff hydraulic characteristics and sediment yield in gully headcut erosion processes

AbstractVegetation plays a crucial role in gully headcut erosion. However, little is known about how grass influences runoff hydraulics, soil erosion and headcut erosion processes. A series of rainfall and scouring experiments were conducted on four plots to elucidate the effect of the density of Agropyron cristatum (L.) Gaertn (planting spaces: 20 × 20 cm2, GA1; 15 × 15 cm2, GA2; 10 × 10 cm2, GA3; bare land as control, BL) on runoff hydraulics and soil erosion during gully headcut erosion. The velocity, Reynolds number (Re), runoff shear force (τ) and stream power (ω) of the BL increased exponentially with time (P &lt; 0.01). However, for the grassland, most parameters increased linearly with time (P &lt; 0.01). The Froude number (Fr) of the BL and grassland significantly decreased linearly and exponentially, respectively, with time (P &lt; 0.01). For τ, the grass tableland needed to develop for a period of time to restrain it. The runoff of the BL tableland and gully head was supercritical turbulent, while that of the grassland was more dispersed. The existence of a gully head increased the jet velocity by 2.97%–67.19%, which increased the dispersion degree of the runoff. The runoff energy showed a significant exponential increase with time (P &lt; 0.05). Compared with that of the BL, the energy consumption of the runoff from the grassland increased by 4.10%–31.81%. During gully headcut erosion, the BL was primarily cut down to the tableland by runoff, while the grassland was cut down to the headwall by on‐wall flow. As the density increased, the benefit of sediment reduction increased, reaching a maximum of 66.79%. The collapse of the BL primarily occurred in the upper part of the headwall during the early experimental stage. The frequency and space–time ranges of the collapse of the grassland were larger than those of the BL. The gravity erosion types of the BL were headwall collapse and gully bank collapse, while those of the grasslands were headwall collapse and root‐soil composite collapse.

Dynamic Evolution and Quantitative Attribution of Soil Erosion Based on Slope Units: A Case Study of a Karst Plateau-Gorge Area in SW China

Exploring the dynamics of soil erosion and identifying its driving mechanisms is key to understanding soil erosion processes, particularly in karst areas. In this study, the RUSLE model, optimized on the basis of rocky desertification factors, was used to estimate soil erosion in a karst plateau gorge area in SW China. The spatial and temporal dynamics of soil erosion in the region over the past 20 years were analyzed on the basis of slope units, while the relationship between soil erosion and elevation, slope, fractional vegetation cover (FVC), karst rocky desertification (KRD), rainfall, and land use cover/change (LUCC) was identified quantitatively by the geographical detector on the basis of spatial heterogeneity. The results showed that: (1) The no erosion area decreased from 2000 to 2020, with the highest proportion of light to medium erosion and an increasing trend of soil erosion. (2) Soil erosion conversion mainly occurred between no erosion, slight erosion, and light erosion. (3) The hotspots of erosion occurred in high slope–low elevation and high slope–high elevation units, while the coldspots of erosion occurred in low slope–low elevation units. (4) Soil erosion was positively correlated with FVC and slope, and negatively correlated with KRD. (5) The dominant factor of soil erosion changed from KRD-slope to LUCC-slope and finally to elevation-slope, while the q value of rainfall-elevation had the most significant increase throughout the study period. This study will help to advance the goal of sustainable development of soil and water conservation in karst areas.

Effects of sediment characteristics on the sediment transport capacity of overland flow

The transport of sediments is a crucial part of soil erosion. Accurately calculating the sediment transport capacity is key to the construction of soil erosion process models. Research on Tc has focused mainly on the dynamics of a single particle of sediment and hydraulic variables. There have been few studies of the impact of soil aggregates on the Tc. To clarify how sediment characteristics, including those for single particles and aggregates, affect the Tc of overland flow with no raindrop import, flume experiments were implemented at slope gradients varying from 5.24% to 26.80% and flow discharges ranging from 0.68 to 5.41 × 10−3 m2 s−1. The experimental materials were five typical soils in China. The results indicated that the correlation between the measured Tc and sediment mechanical composition indexes of the five soils was indistinctive in this study. The sediment settling velocity with aggregates has a significant correlation with the measured Tc. New equations, including for the sediment settling velocity with aggregates ωud75, were established to calculate the Tc. The empirical equation that included ωud75, slope gradient and unit discharge performed greatly in predicting Tc (R2 = 0.93, NSE = 0.90). ωud75 can effectively improve the calculation accuracy of Tc. The new equation including flow and sediment properties obtained through dimensional analysis performed well in predicting Tc (R2 = 0.99, NSE = 0.91), and the calculation accuracy was better than that of the empirical model derived in this study. These findings indicate that the sediment settling velocity is an important variable in the equation for predicting sediment transport capacity of overland flow.

Remote Sensing Quantitative Research on Soil Erosion in the Upper Reaches of the Minjiang River

The upper reaches of the Minjiang River are an important ecological barrier to the upper reaches of the Yangtze River and Chengdu Plain. They are also the water resources of Chengdu Plain. To protect the headwater ecosystems, it is necessary to carry out quantitative research on soil erosion in this area. This study mainly applies the USLE model to quantitatively evaluate the spatial distribution of ecosystem services on soil erosion and soil conservation. The evaluation is based on the following data: remote sensing image, meteorological radiation data, DEM, soil types, physical and chemical properties of the soil, vegetation types, and land use status. With advanced Earth observation technology, satellite remote sensing images about terrestrial vegetation and other evaluation parameters can be obtained in real time. The seasonal changes in vegetation coverage and the physical and chemical properties of soil have been fully considered. The results show that 1) the value of rainfall erosivity factor (R) is between 85.02 and 588.69 MJ•mm/(hm2•h•a), and its spatial distribution is consistent with that of annual average precipitation. 2) Soil erodibility factor (K) is between 0.12 and 0.30 (t hm2 h) •(hm2 MJ mm), showing zonal distribution, and is related to soil types. 3) Slope length and gradient factor (LS) range from 0.03 to 46.16. It is positively correlated with topographic relief. 4) Soil conservation measure factor (P) ranges from 0 to 1 and is determined by the land use and coverage. 5) Rainfall has a dominant impact on soil erosion, and the study area with violent and intense erosion reaches 17,302.17 km2, accounting for 69.81% of the total area. The soil conservation amount (T) in the study area is 283.45 million tons, and the ecosystem services are worth 434.48 million yuan. 6) RS and GIS techniques enable quick estimation. However, this assessment contains considerable uncertainty. It is still hard to reveal the physical process of soil erosion with empirical models.

Soil Erosion Process Simulation and Factor Analysis of Jihe Basin

Soil erosion is a notable contributor to carbon emissions. Distributed erosion model can be used to study erosion distribution in different land cover, identify the main influential factors, and hence guide soil and water conservation. In this study, Regional Soil Erosion model (RSEM) was used to simulate the soil erosion processes of Jihe Basin in 2015, and the Multiscale Geographically Weighted Regression (MGWR) implementation was applied to compare the erosion regression of Geographically Weighted Regression (GWR) and MGWR as well as study the impact of influential factors on sediment modulus in hillslopes. The results are as follows: (1) MGWR results indicated slope was the dominant factors affecting soil erosion at the catchment scales, where the average coefficients of slope, forest coverage, and grass coverage descended in the value of 0.90, −0.11, and −0.19, and the influences of factors operate over scales; (2) MGWR with the adoptive bandwidths performed well in the goodness of fit, t-test of variables, scales that variables operate, and interactive interpretation of soil erosion; (3) the coupling effects and scales of vegetation and topography factors are an important approach to study soil erosion at a larger scale.