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Abstract In Southwest China (SWC) soil loss is becoming a serious threat to the sustainable development of resources and the health of the environment. A large number of studies have been conducted to investigate the causes (e.g. environmental factors and human activities) and impacts (e.g. karst rocky desertification) of soil loss. However, the following are some important problems related to soil loss in the karst of SWC: 1) although soil loss is caused by chemical weathering, gravity and water interaction in karst, the mechanisms by which soil loss takes place in the SWC and their interaction are still not clear; 2) subsurface soil loss varies under different geological and hydrological conditions, and there is still no consensus on the common the ratio between surface soil erosion and underground soil loss; 3) traditional methods for soil loss risk assessment are difficult to apply over the whole of SWC; and 4) a large number of studies have been published only in Chinese and remain inaccessible to the international science community. Therefore, a review paper is needed to address this gap and introduce the contributions of Chinese researchers to soil loss in karst. This paper proposes a novel modelling approach for the grouped soil loss styles and presents a comprehensive discussion for the mechanism, causes, and risk assessment of the various soil loss styles in SWC karst. Graphical abstract Unlabelled Image Highlights • Soil is eroded not only in the surface but also in the underground rock layer. • Surface/subsurface soil loss and soil leakage are typical soil loss styles in karst. • Novel modelling is proposed to discretize the grouped soil loss styles in karst. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of soil erodibility is an essential requirement for erosion prediction, conservation planning, and the assessment of sediment related environmental effects of watershed agricultural practices. This paper reviews the status of soil erodibility evaluations and determinations based on 80years of upland area erosion research mainly in China and the USA. The review synthesizes the general research progress made by discussing the basic concepts of erodibility and its evaluation, determination, and prediction as well as knowledge of its spatio-temporal variations. The authors found that soil erodibility is often inappropriately or inaccurately applied in describing soil loss caused by different soil erosion component processes and mechanisms. Soil erodibility indicators were related to intrinsic soil properties and exogenic erosional forces, measurements, and calculations. The present review describes major needs including: (1) improved definition of erodibility, (2) modified erodibility determinations in erosion models, especially for specific geographical locations and in the context of different erosion sub-processes, (3) advanced methodologies for quantifying erodibilities of different soil erosion sub-processes, and (4) a better understanding of the mechanism that causes temporal variations in soil erodibility. The review also provides a more rational basis for future research on soil erodibility and supports predictive modeling of soil erosion processes and the development of improved conservation practices. [Copyright &y& Elsevier]

Abstract: Following construction of the Three Gorges Dam, many farmers resettled in surrounding mountain areas and cultivated marginal lands, which are mostly on steep slopes with soil of poor structure. In general, high soil loss rates occur during intense storms. Therefore, soil erosion is a major environmental problem in the Three Gorges area (TGA) of China. Understanding and quantifying sediment load is important for sustainable agriculture and the environment in this region. This paper analyzes the relationships between rainfall, runoff, and sediment transport in the Wangjiaqiao watershed. Strong seasonal and monthly variability in sediment load was found. Sediment was strongly transported during summer months, a period when frequent flood events of high magnitude and intensity occurred. Analysis of the relationships between precipitation, discharge and sediment transport at an individual event scale showed significant correlations between total precipitation, peak discharge, total water yield, maximum 30min rainfall intensity, and sediment-related variables. Stepwise multiple regression analysis revealed that rainfall amount is the major cause of runoff, while events producing a large discharge in a short time play an important role in inducing severe soil erosion. During 40 flood events, three different types of hysteretic loops were observed: clockwise (28 events, 70%), figure-eight (5 events, 12.5%), and complex (7 events, 17.5%). The results of this study confirm the complex and heterogeneous nature of sediment response in the Wangjiaqiao watershed. [Copyright &y& Elsevier]

Abstract: In the previous studies, a method was developed to assess soil erosion based on land use information. In this paper, we present another approach that uses environmental data to assess soil erosion. A soil erosion characteristic index EI is proposed, and its value is derived using the Analytic Hierarchy Process (AHP) technique based on standardized environmental information stored in minimum polygons that tile the erodible area under consideration. The approach is applied to a case study of the Yellow River basin, north China, where serious erosion is occurring. To represent different grades of soil erosion, the range of EI is divided into six levels according to standard grades of soil erosion intensity. The application indicates that the method deals properly with data scarcity, with the results giving a satisfactory representation of the characteristics of soil erosion in the Yellow River basin. The spatial–temporal distribution of EI in the Yellow River basin is predicted, and the results interpreted to give the long-term trend and state of soil depletion. Comparisons are given between EI and surveyed soil erosion zoning maps for the Yellow River basin at the end of the 1980s and 1990s. The output reliability and the approach applicability in smaller spatial scales are investigated in a case study of Zhifanggou basin. [Copyright &y& Elsevier]

Abstract: Intensive anthropogenic disturbances have affected the channel of the middle Yangtze River since the 1950s. This paper selects the Jianli reach as an example to examine human impact on channel change in the middle Yangtze River. 1:100,000 channel distribution maps from 1951, 1961 and 1975 and 1:25,000 navigation charts from 1981 and 1997 were employed to reconstruct channel change in the study reach. The result indicates that the channel, under the constraint of levees along the riverbanks, underwent a minor widening but frequent bank failure due to susceptible bank structure and increase in water discharge. The bank failure promoted bar growth in the channel. Cross-section changes and quantitative calculations of erosion and deposition based on the DEM derived from navigation charts present a pattern of over-bank sedimentation and riverbed incision. The stage and duration of floods have increased following levee construction and bank revetment. [Copyright &y& Elsevier]

A Holocene loess profile to the west of Xi''an China was studied multi-disciplinarily to investigate the relationships between soil erosion and monsoonal climatic change. The proxy data obtained from this aeolian loess and palaeosol sequence indicate large-scale variations of climate in the southern Loess Plateau since the last glaciation. A rainwash bed, indicative of a wetter climate, excessive runoff and erosion on the loess tablelands, was identified relating to the early Holocene before the onset of the “climatic optimum”. This is synchronous with the early Holocene physiographic erosional stage identified in the valleys in North China. It means that severe erosion took place when the region was undergoing climatic amelioration during the early Holocene. The evidence presented in this paper shows that the erosion occurred as a regional response to a monsoonal climatic shift in the southern Loess Plateau. During the last glaciation, prior to the erosion phase, the land surface on the tablelands had been largely stable except for the rapid accumulation of aeolian dust and the resultant increase in its elevation. Relatively slow dust accumulation and intensive bio-pedogenesis responding to the Holocene “climatic optimum” followed the erosion phase. The loess tablelands were most vulnerable to erosion during the large-scale monsoonal climatic shift from dry-cold glacial to humid-warm post-glacial conditions in the southern Loess Plateau. [Copyright &y& Elsevier]

Loess caves, landslides, collapses, bank erosion and soil erosion, which are independently and interactively shaping the modern loess landscape, are widely distributed across the Chinese Loess Plateau. The study area is located in a small watershed in Huining County, Gansu Province, which is one of the areas with the strongest development of loess caves across the Loess Plateau. This area is an ideal site for studying geological hazards and geomorphic evolution on the Loess Plateau. Seventeen landslides and 176 loess caves with a density of 887 units/km2 were investigated with a UAV (unmanned aerial vehicle) and mapped by GIS (geographic information system). Using high-resolution UAV images and topographic data, we carried out an interpretation of loess caves, bank erosion and landslides; studied the spatial distribution and developmental patterns of loess caves, landform morphology and the relationship between loess caves and landslides based on GIS spatial analysis, mathematical statistics and field surveys; and analyzed the influence of loess microtopography on slope landforms. Finally, six typical evolutionary models of soil erosion-loess cave development-landslide occurrence-barrier dam formation are preliminarily proposed: the primary slope stage, early cave stage, accelerated cave stage, cave connecting stage, landslide creeping stage, and landslide-dam forming stage. This study is a useful exploration and an attempt to reveal the influence of loess cave development on slope stability and disaster chain effects. • This paper completed the high-resolution interpretation of loess geological hazards based on UAV. • Spatial distribution, developmental regularity and influences of loess caves were revealed. • Typical evolution model of the loess disaster chain was preliminarily proposed. [ABSTRACT FROM AUTHOR]