微地形空间离散化水文响应单元确定方法

空间离散化是分布式水文模型构建的充要条件。在90 mm/h雨强人工降雨试验、三维激光扫描构建微地形数字高程模型(M-DEM)的基础上,基于元胞自动机(CA)模型研究了人工掏挖微地形在5种不同坡度条件下侵蚀发育过程中不同大小格网/元胞的水沙汇集和传递关系,进而提出空间离散化水文响应单元(HRU)的确定方法。结果表明:基于CA模型所确定的5°,10°,15°,20°和25°坡在溅蚀阶段的最佳HRU大小为6 mm,5 mm,6 mm,5 mm,8 mm; 片蚀阶段的最佳HRU大小为6 mm,4 mm,6 mm,5 mm,5 mm,细沟侵蚀阶段的最佳HRU大小为4 mm,7 mm,5 mm,6 mm,6 mm,纳什效率系数均接近于1; 综合以上,90 mm/h雨强下人工掏挖微地形水蚀模拟最佳HRU应为6 mm。研究提出了一种微地形空间离散化的方法,为微地形尺度水蚀定量化研究提供了一定的技术支撑。

Method of Determining Hydrological Response Units for Discretization of Microtopography

Spatial discretization is a necessary and sufficient condition for the construction of distributed hydrological models.Based on the 90 mm/h rain intensity artificial rainfall test and three-dimensional laser scanning to construct the digital elevation model of micro-topography(M-DEM),and the cellular automata(CA)model,the water-sediment collection and transfer relationship of different size grids/cells in the process of erosion development in the artificially excavated micro-topography on 5 different types of slopes were studied,and then a method for determining spatial discretization hydrological response unit(HRU)was proposed.The results show that the optimal HRU sizes for the 5°,10°,15°,20°and 25°slopes determined by the CA model in the splash phase are 6 mm,5 mm,6 mm,5 mm,8 mm;the best HRU sizes at the sheet corrosion stage are 6 mm,4 mm,6 mm,5 mm,5 mm;the best HRU sizes for the rill erosion stage are 4 mm,7 mm,5 mm,6 mm,6 mm;the Nash efficiency coefficients are all close to 1.Comprehensively above,the best HRU for water erosion simulation of artificially excavated micro-terrain should be 6 mm under the rainfall intensity of 90 mm/h.This study puts forward a method for the spatial discretization of micro-topography,which can provide certain technical support for the quantitative study of water erosion at the micro-topography scale.