考虑河底比降的等流时线划分方法

Using the Gradient of River Bed to Plot Isochronic Lines of Watersheds

本文针对等流时线间距离确定问题,考虑干流河段汇流时间、流速、流程和河底比降等因素,推导出新的适用于干流河段的等流时线间距的计算公式。由于支流的河长及其河底比降与干流的河长及其河底比降不相同,因此,本文还推导出适合支流的等流时线划分公式。在实际应用中,采用数字高程模型(DEM)确定河底高程,进而计算河底比降。本文将建议的新的等流时线划分方法应用于南河开峰峪流域汇流计算中,结果表明新的方法具有较好的精度。

The existed methods to determine the distance between the isochronic lines are commonly based on the speed or time of concentration of watersheds.Because the distance between the isochronic lines is usually considered as a constant value,the isochronic lines with the constant distance are essentially isometric lines.In this paper,new formulations,considering the time of concentration,flow speed,flow distance and the gradient of river bed,were derived for the reach of main stream.Because of the differences of stream length and the gradient of river bed between main stream and branch stream,the formulations suitable to branch stream were also given.Based on DEM（Digital Elevation Model）,the elevations and gradients of river bed were obtained and calculated.The suggested new methods were used in the flow routing of Kaifengyu catchment of the Nanhe River,and compared with the existed methods.The results show that the accuracy is improved by using these suggested new methods.