汶川地震灾区小流域洪水计算方法初探

汶川地震灾区小流域山洪不仅造成巨大损失,同时也是泥石流等灾害的激发因素,探寻一种准确且可操作的洪水峰值流量计算方法对防灾减灾具有重要意义。本文选择不同产流和汇流计算方法,组合成不同水文模型,进行小流域洪水过程计算,对模拟结果和参数选择进行对比,旨在探究最适合该地区的小流域水文计算方法。分别选择SCS曲线法、Green-Ampt入渗法、初损稳渗法进行坡面产流计算,应用SCS单位线法、Snyder单位线法和运动波方程进行坡面和沟道汇流计算,组合成5种小流域产汇流计算模型,利用6场洪水进行参数率定和结果验证。模拟结果对比分析,得出SCS曲线法是最适宜的产流模型,其与SCS单位线、运动波汇流计算方法组合而成的SCS和SKK模型,峰现时间的模拟误差最小,在0~25 min之间;洪峰流量模拟的相对误差较小,平均误差不超过4%;洪水总量模拟误差在10%左右。另外,这两种模型参数设置及确定较简单,更适合在数据稀缺的小流域中进行洪水模拟应用。研究可为汶川地震灾区小流域山洪和泥石流等灾害的流量估算提供方法和参数借鉴。

Study on the discharge calculation in small watershed in Wenchuan earthquake area

Mountain torrents not only cause huge losses,but also are the inducing factors for debris flows in small watersheds in the Wenchuan earthquake-stricken area.It is of great significance to find an accurate and operable method for calculating the flood discharge for disaster mitigation.This work aims to investigate the efficiency of different hydrological models which are commonly used,and to find the most proper methods for peak discharge calculation.The methods selected for slope runoff yield calculation include the SCS Curve Number method,Green-Ampt method and the Initial and Constant method,and methods for influx process include SCS Unit Hydrograph method,Snyder Unit Hydrograph and Kinematic Wave method.Five models are built and the simulation results are investigated.It is found that the SCS Curve Number method is the most suitable model for runoff yield calculation.The models which are combined it with the SCS Unit Hydrograph method,and the Kinematic Wave method,simulate the peak appearance time most accurately with the error range of 0-25 min,and the relative errors of peak discharge and total volume are smaller than 4%and about 10%,respectively.In addition,the parameters of the two models are determined simply,and are more suitable for flood simulation in small watersheds with scarce data.The research can provide methods for the flow estimation in the small watershed of the Wenchuan earthquake area.