DEM-based Numerical Modelling of Runoff and Soil Erosion Processes in the Hilly–Gully Loess Regions

The Loess Plateau, located in the middle Yellow River basin of China, has been commonly reported for the most serious soil erosion and water losses all over the world. Due to a vast cover area (640,000 km²) and very rich coal resource, the Loess Plateau is very important to regional eco-environmental security and the sustainable development of western China. For this purpose, modeling of runoff and sediment processes are of paramount importance to understanding the soil erosion processes and formulating effective countermeasures for soil erosion control for the region.

Physically-based models such as ANSWERS, WEPP, EUROSEM, GUEST, and LISEM are now widely accepted mathematical models for simulating soil erosion processes, but they cannot be applied directly to simulate runoff and sediment yield processes on the hilly and gully-covered Loess Plateau of China. Furthermore, some improved models such as the Hohai University Model (HUM) still have several critical limitations when they are used in a loess region.

Based on the previous studies, professor YANG Tao and other researchers developed a digital elevation model (DEM)-based runoff and sediment processes simulating model for sake of improving the current understanding on soil erosion processes in the hilly–gully loess regions of the middle Yellow River basin in China. Infiltration excess runoff theory was used to describe the runoff generation process while a kinematic wave equation was solved using the finite-difference technique to simulate concentration processes on hillslopes. The soil erosion processes were modelled using the particular characteristics of loess slope, gully slope, and groove to characterize the unique features of steep hillslopes and a large variety of gullies based on a number of experiments. The constructed model was calibrated and verified in the Chabagou catchment, located in the middle Yellow River of China and dominated by an extreme soil-erosion rate. Moreover, spatio-temporal characterization of the soil erosion processes in small catchments and in-depth analysis between discharge and sediment concentration for the hyper-concentrated flows were addressed in detail. Thereafter, the calibrated model was applied to the Xingzihe catchment, which is dominated by similar soil erosion processes in the Yellow River basin.

Results indicate that the model is capable of simulating runoff and soil erosion processes in such hilly–gully loess regions. The developed model are expected to contribute to further understanding of runoff generation and soil erosion processes in small catchments characterized by steep hillslopes, a large variety of gullies, and hyper-concentrated flow, and will be beneficial to water and soil conservation planning and management for catchments dealing with serious water and soil loss in the Loess Plateau.

The result has been published on Stochastic Environmental Research and Risk Assessment, 2012, 26: 581-597. The paper is also archived at http://www.springerlink.com/content/h534103246p81371/.