集水面积阈值确定方法的比较研究

Identification and Comparison of Critical Support Area in Extracting Drainage Network from DEM

针对坡面径流模拟算法引入集水面积阈值划分流域内的河网与坡地直接影响了生成的数字河网精度,探讨并比较了多种推求流域集水面积阈值的方法。结果表明,各种方法可互补;采用集水面积与河道平均坡降关系和采用集水面积与河网密度曲线具有较好的一致性;流域面积越大,采用宽度分布推求阈值准确,流域面积越小,采用水系分形推求阈值准确;集水面积阈值在流域内各处并非完全相同,应考虑采用多个阈值。

The critical support area, as a vital parameter in the method, defines the minimum drainage area required to divide hillslopes and channels and ultimately has its impact on the precision of extracted drainage network. Four methods for identifying critical support area are discussed and compared in this paper, including the relation between contributing area and topographic slope, the drainage network density method, the width function method and the fractal method. The computed results show that the above ways of identifying critical support area can be complementary. The result from the relation between contributing area and topographic slope is in good agreement with that computed by the method of drainage network density. The river width function method is more suitable in larger catchment while the fractal method is appropriate in small watershed. Thus it is recognized that different values of critical support areas should be specified within a large scale of catchment because of spatial variability.