汶川地震灾区小流域洪水模拟及不确定性分析

Uncertainty analysis of hydrological model in the application of small watershed in Wenchuan earthquake disaster area

2008年汶川地震以来,灾区山洪泥石流等次生灾害频发,山区洪水不仅自身具有极大危害,也是激发泥石流等次生灾害的水源条件。采取科学有效的方法对洪水流量进行估算,对于山洪和泥石流防灾减灾具有重要科学和现实意义。本文选取震区一个具有数年监测历史的小流域(2.4 km2)为研究对象,选取具有代表性的降雨场次,利用SCS产流模型和运动波方程分别进行产流和汇流计算,模拟洪水过程,用实测数据验证该水文模型在研究区的模拟效果。结果表明,该模型可以较好地捕捉峰值流量和峰现时间等关键指标;对于数平方公里尺度的小流域,划分子流域增大了参数选择的难度,对模拟效果并无明显提升;在保持参数一致的情况下,时间步长越短,模拟效果越精确,随着时间步长的增加,峰现时间延迟,洪峰流量减小,径流过程线逐渐坦化,趋于平缓。研究对认识汶川地震灾区小流域产汇流特征和洪水计算方法有一定的科学意义。

Mountainous hazards such as floods and debris flows have occurred frequently in the Wenchuan Earthquake area since 2008. Flash floods not only cause great harm by themselves,but also act as the triggering factors that stimulate the debris flows. Using scientific and effective methods to estimate flood discharge is of great scientific and practical significance for the hazards prevention and reduction. In this work,a small watershed(2.4 km2)with a monitoring history of several years in the earthquake area is selected as the research object. SCS runoff model and the Kinematic wave equation we combined to simulate the runoff of 5 rainfall events between 2014 and 2016.The results show that the model can simulate the key indicators including peak discharge and the occurrence time of peak discharge. It is also found that for small watersheds,dividing sub-watersheds increases the difficulty of parameter selection,and does not significantly improve the simulation results. In addition,the time of peak discharge is delayed,the peak discharge is reduced,with the increase of the time step. The research is of scientific significance for understanding the hydrological characteristics,and flood discharge calculation in small watersheds in the Wenchuan earthquake-stricken area.