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In recent years, soil erosion caused by water erosion has gradually increased due to the increase of extreme precipitation. In order to reduce soil erosion caused by extreme precipitation, it is necessary to monitor soil erosion and found out the factors that affect soil erosion under extreme precipitation. The objective of this study was to assess the amount of soil erosion, the damage degree of soil and water conservation measures and benefit evaluation under extreme precipitation in Henan Province. The results indicated that the ridges of terraces in two small watersheds had been damaged to varying degrees. Terraces, as one of soil and water conservation measures, can better preserve soil and water erosion under extreme precipitation. The amount of soil preserved in two small watersheds were 744.50t and 1121.01t. The amount of soil loss in two small watersheds were reduced by 67.67% and 78.63% when terraces existed. The soil conservation amount of vegetation restoration measures in two small watersheds were 2960.23t and 3320.36t. The amount of soil loss in two small watersheds were reduced by 89.27% and 90.98%, when vegetation restoration measures exist. Compared with soil and water conservation engineering measures, vegetation restoration measures can better reduce soil erosion caused by water erosion under extreme precipitation. In addition to the amount of rainfall, the soil and water conservation benefits of terraces were also affected by the width of the terrace, the slope of the terrace, and whether there were vegetation restoration measures in the terrace. [ABSTRACT FROM AUTHOR]

Soil erosion is a major threat to soil resources, causing environmental degradation and contributing to poverty in many parts of the world. Many field experiments have been performed over the past century to study spatio-temporal patterns of soil erosion caused by surface runoff under different environmental conditions. However, these data have never been integrated together in a way that can inform efforts to understand and model soil erosion at different spatial and temporal scales. Here, we designed a database titled AWESOME: Archive for Water Erosion and Sediment Outflow Measurements (Jian et al., 2022). The AWESOME database compiles field measurements of annual soil erosion and sediment yield caused by surface runoff, with data derived from sites around the globe. It includes four soil erosion-related indicators (surface runoff, annual erosion, annual sediment yield, and soil nutrient loss) and more than sixty variables for meta-data that describe the location, climate, soil properties, experimental design (e.g., soil erosion measurement method, field scale, replication), and bibliographic information (e.g., author name and year of publication). Currently, measurements from 1985 geographic sites with unique combinations of longitude and latitude, representing 75 countries, have been compiled into AWESOME. We provide an example of linking AWESOME with an external climate dataset, and identify correlations between soil erosion and several environmental variables. Annual soil erosion rates were most influenced by vegetation type and soil texture group. Annual soil erosion rates exhibited significant negative relationships with plant coverage, soil clay content, soil pH, and soil organic carbon content, and significant positive relationships with annual precipitation and soil bulk density. AWESOME aims to be a freely available, and global framework for compiling field soil erosion and subsequent sediment yield measurements, and to provide data sources to support statistical evaluations, model validation and applications, as well as a better understanding of spatial and temporal patterns of soil erosion. [ABSTRACT FROM AUTHOR]

Exploring overland flow resistance and sediment delivery capacity under different landscape vegetation conditions is critical for better understanding hydrodynamic mechanisms of soil erosion processes and hydrological connectivity on hillslopes. To evaluate flow resistance relations and sediment transport for landscape vegetation coverage and combinate effect of vegetation patches, field simulated rainfall experiments were conducted using a series of overland runoff and sediment transport rates in 3 m (L) × 2 m (W) experimental plots with coverages of 0%, 20%, 40%, 60% and 90% in a uniformly distributed condition and composited flow paths of different patches (horizonal path, vertical path, random patches and S-shaped path) in the same coverage (40% and 60%). The runoff rates for the grassland with coverages of 20–90% were decreased by 19.3–61.4% (P < 0.05), and the sediment concentrations were reduced by 81.7–97.8% (P < 0.05) compared to the bare land. The Darcy-Weisbach resistance coefficient doubled and the stream power declined by 60.0% when grassland coverage increases to 90%. The runoff rates varied little among the conditions of horizontal, vertical, random and S-shaped flow paths at the coverage of 60%, while the rate apparently reduced by 34.1% (P < 0.05) when the vertical flow path became horizontal under the same coverage of 40%. The sediments for poorly connected flow paths could reduce sediment >90% either on high-coverage or low-coverage grassland. Our field experiments confirmed that the increase of vegetation coverage and the combination of landscape patches could significantly reduce runoff rates, sediment yields and flow velocities, increase surface roughness, promote flow resistance and diminish hydraulic shear stress and the stream power. The poorly-connected paths (horizontal and random) exhibited a stronger flow resistance and weaker sediment transport capacity than the well-connected paths (vertical and S-shaped). • The runoff and sediment are considerably decreased with the coverage increasing. • The flow resistance to runoff is enhanced by poorly connected flow paths. • The sediment transport is significantly influenced by the different flow paths. • The sediments for poorly connected flow paths could reduce sediment >90%. [ABSTRACT FROM AUTHOR]

Abstract: The Yellow River is globally renowned for its high sediment concentration, primarily because it flows over the Loess Plateau, which suffers from severe land degradation mainly in the soil erosion. Vast sediment flows from the Yellow River into the sea through the Yellow River Delta (YRD), largely shaping the YRD. On the basis of remote sensing images and historical hydrological measurements, we investigated the streamflow‐sediment flux from the Yellow River and the land area changes of YRD region from 1976 to 2016. The relationship between the streamflow‐sediment flux from the Yellow River and the land change rate at the YRD was examined. The changes in shape of different parts of the YRD and their influencing factors were also discussed. The results showed that there is a significant correlation between the land change rate at the Estuary region and streamflow‐sediment flux from the Yellow River. Because of ecological environment constructions on the Loess Plateau, the streamflow‐sediment flux, particularly the sediment flux, underwent a decreasing trend. Along with the collapse of sediment flux, the land area of the YRD and the Estuary region increased before 1998 and decreased afterwards. The solidification projects are of great significance to the protection of the Northern River Beach region, but the decreasing trend of the land degradation rate at the Estuary region is unlikely to change. Our results provided a useful reference for the protection of the YRD and prevention of land degradation in the Yellow River Basin. [ABSTRACT FROM AUTHOR]

Check dam has become an efficient measure to control sediment transport and soil erosion in the gully areas. It plays an important role in soil erosion control and agricultural production in the Loess Plateau. Due to construction of numerous check dams, it is necessary to assess the impact of check dams on runoff and sediment load at basin scale. This study applied the SWAT model to simulate monthly runoff and sediment load in the Huangfuchuan basin in the middle reaches of the Yellow River. Twenty key check dams are coupled to the SWAT model simulation in the calibration (1978-1984) and validation period (1985-1989). The determination coefficient ( R ) and the Nash-Sutcliffe coefficient ( NS) were 0.94 and 0.83 for runoff, and 0.82 and 0.81 for sediment load in the calibration period, respectively. During the validation period, the R and NS were 0.93 and 0.80 for runoff, and 0.90 and 0.83 for sediment load respectively. The results showed that the model simulation was acceptable. Subsequently, the calibrated model was used to examine the effect of check dams on runoff and sediment load between 1990 and 2012. It showed that the increasing check dams contributed 24.8 and 27.7% to the decrease of annual runoff and sediment load during the period of 1990-1999, whereas it reached up to 65.2% for runoff decline and 78.3% for sediment load reduction within 2000-2012. Overall, this study illustrated a case study of the dominant role of check dams on variation of runoff and sediment load in the Huangfuchuan basin. [ABSTRACT FROM AUTHOR]

• The vegetation cover showed great improvement with annual NDVI increasing from 0.46 to 0.63 during 2000–2018. • Vegetation restoration contributed 51.2% of soil erosion decrease in the Loess Plateau. • Terraces decreased 19.4% of soil erosion in the Loess Plateau. Soil erosion exhibited significant decrease due to the implementation of considerable soil and water conservation practices on the Loess Plateau, and further induced less sediment discharged into the Yellow River. However, the influences of these practices on soil erosion have not been comprehensively investigated over large-scale regions. This study analyzed spatiotemporal variation of vegetation cover, and identified the distribution of terraces by using Google Earth remote sensing images in the whole Loess Plateau. The USLE model (Universal Soil Loss Equation) was applied to estimate responses of soil erosion to vegetation restoration and terraces. The annual regional-averaged NDVI increased from of 0.46 in 2000 to 0.63 in 2018, suggesting significant vegetation improvement due to afforestation. We detected 4.73 × 104 km2 of terraces by 2018, which covered approximately 1.5% of the whole Loess Plateau. The terraces were mainly distributed in the upstream of the Weihe River, Fenhe, Zuli, Jinghe, and Taohe River basins. The validated soil erosion model showed that vegetation changes caused a remarkable reduction of 51.2% soil erosion from 2000 to 2018 across the Loess Plateau. A scenario modelling with terraces reduced 19.4% of soil erosion, indicating their significant effects on soil erosion controlling. This study could give a useful reference to assess soil erosion changes response to vegetation restoration and terrace at a large scale. The results can be used to optimize the spatial layout of the measures for soil erosion control in the Loess Plateau in the future. [ABSTRACT FROM AUTHOR]

• Conservativeness and consistency for individual tracer were evaluated. • The optimal tracers set varied in different flood process. • Bare land was the predominant source to the total sediment load within flood events. • The weathered sandstone area is the critical region for soil loss control. Identifying critical soil erosion areas and sediment sources are essential for sediment control and water resources management in the watershed, especially in the severely eroded northern Loess Plateau, China. In this study, we collected suspended sediment samples at the hydrological stations to identify the sediment source dynamics during flood events in a highly erodible basin, the Huangfu River basin in the Northern Loess Plateau. A total of 6 flood events were sampled during 2016 and 2018 for investigation, the flow discharge was featured by a rapid rising limb and a slow falling limb. Compared with the sediment sources, the silt fraction in the suspended sediments was enriched and the sand fraction in the suspended sediment was depleted. The dominant particle grain size of suspended sediments was coarse sand (56.89%), higher than silt (41.81%) and clay (1.3%). The sediment sources were estimated using the FingerPro unmixing model based on the conservativeness index (CI) and consensus ranking (CR) methods. The results of the unmixing model reveal that the bare land was the predominant source of suspended sediments, ranging from 40% to 57%, which was much higher than farmland (27 ∼ 31%) and grassland (16 ∼ 25%). Our findings imply that the bare land (weathered sandstone area) is the critical region for soil loss control in the Huangfu River basin. A combination of vegetation restoration measures and engineering measures are proposed to improve the sustainable development of ecological environment in the basin. [ABSTRACT FROM AUTHOR]

An improved understanding of the temporal variations in soil erosion rates and sediment sources is necessary to identify the main areas prone to soil erosion and to effectively implement soil and water conservation measures. In this study, we selected two dam-controlled watersheds (Xiaoshilata and Yangjiagou) on the northern Loess Plateau, China, and determined the temporal variations in the sediment yield. The sedimentation upstream of the dams showed that there were 31 and 9 flood couplets in the Xiaoshilata (1958–1972) and Yangjiagou watersheds (2007–2011), respectively, which have trapped 16.5 × 10 4 t and 3.38 × 10 4 t of sediment, respectively. The estimated specific sediment yield was approximately 173.6 t/ha/a and 106.1 t/ha/a in the Xiaoshilata and Yangjiagou watersheds, respectively. A multivariate mixed model was applied to identify the different sediment sources. The results indicated that weathered sandstone contributed approximately 61.52% of the total sediment, and the remaining sediment loss was from bare loess soil (32.54%) and grassland (5.94%) in the Xiaoshilata watershed. In the Yangjiagou watershed, approximately 66.8% of the sediment originated from weathered sandstone, whereas bare loess and grassland accounted for 17.5% and 15.7% of the sediment yield, respectively. Based on these findings, we recommend that comprehensive soil conservation measures are needed to soil erosion control for the permanent steep gullies due to high sediment contribution. The sedimentation behind the check dams provides an indirect method for estimating the sediment yield in ungauged basins. [ABSTRACT FROM AUTHOR]

Large-scale sediment control efforts on the Loess Plateau of China and resulting reductions in sediment yield have been documented. However, it remains unclear how these control works affect the soil erosion rates and sediment loads at the catchment scale. A combination of field work and modeling exercises was used to examine the effects of land use changes and check dams on the variation of sediment yield at the catchment scale. The Huangfuchuan catchment was selected as a case study. The sediment distributed delivery (SEDD) model was calibrated using both observed sediment load data and sedimentation rates derived from check dams. The study catchment suffered important land use changes with increasing grassland and decreasing bare land, sandy area and arable land from 1990 to 2006. By 2009, 502 check dams with a total storage capacity of 571 Mm 3 had been built in the study area. Relatively good agreement can be seen between observations and model simulation results. Model applications showed that in a scenario without check dams, the land use changes between 1990 and 2006 caused a remarkable reduction of 31.4% in sediment yield. The check dams without land use changes with respect to the 1990 scenario reduced 51.9% of the sediment yield in the study area. The combination of land uses and check dam construction in 2006 reduced the sediment yield by approximately 80%. Our results indicate that check dams are efficient sediment control measures; however, the accumulation of sediment in check dams may create costly problems in the operation of dams and failures because of their short lives. Therefore, sustainable solutions are needed for sediment management in the check dams, such as sediment pass-through, flushing, or mechanical removal, and a reasonable construction plan is also needed for flood control. [ABSTRACT FROM AUTHOR]

Soil erosion is a major form of land degradation throughout the world and the key environmental problem that threatens the ecosystem of the Chinese Loess Plateau. In this study, we determined the sediment yield from a small dam-controlled watershed in the Huangfuchuan watershed, northern Loess Plateau, with a drainage area of 0.64 km 2 . The dam infill sediment provided evidence of at least 31 flood couplets, which corresponded to rain storms during 1958–1972. In total, 1.65 × 10 5 t sediment was accumulated within the whole check dams in this period. The annual sediment yield ranged from null in 1965 to 59,990 t in 1959. We used the modified WATEM/SEDEM model to simulate soil erosion and the sediment yield in the watershed and the sedimentation records were used for model verification. The model produced satisfactory results; the total soil erosion and sediment delivery ratio were estimated to be 1.97 × 10 5 t and 83.6%, respectively. Bare weathered stone in the steep gullies contributed > 90% of the sediment yield, while the remainder was derived mainly from bare loess slopes and the alluvial plain. This study suggests that analyzing sedimentation behind check dams and applying the WATEM/SEDEM model are useful for the quantitative analysis of sediment dynamics in ungauged basins on the Loess Plateau. [ABSTRACT FROM AUTHOR]

• A connectivity index was coupled with a soil erosion model to estimate sediment yield. • Afforestation led to evident decreases in both the connectivity and the sediment delivery ratio. • The modeled sediment yield showed a 60.7% reduction due to changes in land use and check dams. The hydrological connectivity on the Loess Plateau has been greatly altered by soil and water conservation measures in the past six decades, leading to significant reduction in sediment load. Nevertheless, how these measures affect sediment transport at the catchment scale remains unclear. This study coupled an index of connectivity (IC) with the Revised Universal Soil Loss Equation (RUSLE) model to estimate the sediment yield in the Yanhe catchment (7,725 km2). The model was used to assess the impacts of land use changes and check dam construction on sediment delivery. The land use maps showed increasing grassland (10.3%) and decreasing arable land (12.3%) from 1990 to 2010. The ranges of IC between the two land use scenarios showed significant changes with an average of 0.3 in 1990 and −0.5 in 2010. Land use changes resulted in average sediment delivery ratio decreasing from 0.39 in 1990 to 0.30 in 2010. The model was calibrated by annual sediment load at a gauging station, covering 5,852 km2 of the catchment and by sedimentation rates behind check dams in a representative sub-catchment. Measured and simulated sediment load showed consistent agreement, suggesting acceptable model performance. An approximately 60.7% reduction in sediment yield was attributed to land use changes and increasing check dams′ construction from 1990 to 2010. This study provided a good example of combining the IC with a soil erosion model to identify spatial patterns and temporal variations in sediment yield due to soil conservation measures. [ABSTRACT FROM AUTHOR]