全流域逐地块水土流失计算,是目前水土保持定量评价的重要手段,其实现过程既需要有考虑地貌因子和上下游关系的土壤侵蚀模型,也需要建立全流域地块汇流网络,并与侵蚀模型有机连接。本文针对黄土高原特殊的地理条件和水土流失规律,对传统的基于栅格的小流域汇流技术进行了改进,考虑地块间上下游汇流关系,建立了基于地块的水沙汇流网络模型,模拟水沙在流域复杂下垫面的汇流过程,提取出流域各地块间的水沙汇流网络,并计算出3个重要参数:流域地块间水沙汇流的顺序、流域地块间水沙汇流数目的空间分配、水沙流经各地块的坡长。将土壤侵蚀模型按地貌部位与特征分为坡面模型、沟坡模型和沟道输移模型,与地块汇流网络有机集成,实现了水沙运移的全流域按地块沿程计算。

To calculate soil erosion based on landunit in a catchment is a new and important method for estimation of soil and water conservation measuresTo achieve such a process based calculation in a catchment or a basin, soil erosion model with both landform factors and up and down stream relations in a catchment need to be developedMeanwhile, the runoff flow networks among landunits, which indicate the relations of runoff flow paths between landunits, are necessaryThe flow networks must be connected with soil erosion models to fit the model principlesIn this paper, the traditional technology of grid based flow network was improved according to loess soil erosion rolesA landunit based runoff and sediment flow network model was developed for simulating the flow process in whole basin, from top of basin to its outletThe flow network among landunit was calculated and three important parameters for soil erosion model were afforded: water and sediment flow order among landunits; the spatial distribution of the conflux amount among landunits; and the slope length of the runoff and sediment passing through each landunitThe soil erosion model was developed according to field observation of natural rainfall and artificial rainfalls with different slope, various land cover and different soil conditionsThe model was divided into three models according to landform positions: flat slope model for areas where the slope of landunit is less than 5 degree; slope model for simulation in whole slope; and gully bottom model for calculation of sediments transfer to the outletThese three models were connected with the landunit flow networks, and the parameters for each landunit such as soil type, slope, elevation, vegetation coverage, cultivating measures, landform position, slope length, etc, were automatically transferred from landunit file to the soil erosion model.