GIS支持下的小流域设计洪水过程线推求

Calculation of Design Flood Hydrograph for Small Watershed Based on GIS

浙江省衢州庙源溪为典型的山区河流,庙源溪雨量丰富,河流比降大,源短流急,洪水陡涨陡落,汇流速度快,洪峰流量大。基于GIS的不规则三角网和空间分析功能,实现水文特征值等值线的内插。根据GIS获取的水文特征值,计算不同历时平均点雨量,考虑点面折算系数,得到平均面雨量。通过频率分析,获得不同频率下的设计雨量。采用瞬时单位线法,进行汇流计算,推求设计洪水过程线及洪峰流量,为制作山洪风险图,建立小流域防洪避洪保障体系提供依据。

The Miaoyuanxi River, located in Quzhou City of Zhejiang province, is a typical mountain stream. The river has characteristics of plentiful rainfall, steep gradient, short source and swift flow, sudden flood rising and sharp dropping, quick travel speed, and great peak dis- charge. The triangulated irregular network and spatial analysis function of geographic information system（GIS） were analyzed to realize interpo- lation of the isoline of hydrological statistical parameters. According to the hydrological characteristic parameter derived from GIS, the average point rainfall at different duration was calculated. In view of conversion coefficient of point rainfall into area rainfall, the average area rainfall was obtained. By frequency analysis, design rainfall at different frequency was calculated. The instantaneous unit hydrograph was applied to carry out convergence computation and infer design flood hydrograph and peak flow, which provide basis for drawing mountain flood risk map and establishing security system for small watershed flood control and flood evasion.