岷江上游汶川地震重灾区山洪灾害危险分区研究

Flash Flood Risk Zoning of Areas Hit by Wenchuan Earthquake in the Upper Reach of Minjiang River

以岷江上游汶川地震重灾区为靶区,在剖析山洪灾害特征及驱动因子的基础上,开展山洪灾害危险性分区研究。得出研究区山洪灾害具有如下特征:1受暴雨控制,主要分布在龙门山暴雨区,具带状、群发特征;2受地震发震断层的控制,在主断层范围内集中、连片分布;3呈串联或并联特征;4震后崩塌、滑坡淤堵河道,山洪灾害发生的临界雨量降低,导致山洪灾害规模扩大、频率增加,危害加剧。根据主控驱动因子即暴雨驱动因子(年最大1 h暴雨均值)和地震驱动因子(距发震断层距离),将研究区山洪灾害分为3个等级:高度危险区、中度危险区和低度危险区。研究成果可为岷江上游流域山洪灾害的监测预警、综合防治、减少山洪灾害损失等提供依据。

With the Wenchuan earthquake-hit area in the upper reach of Minjiang River as the study area, the char- acteristics of flash flood disaster distribution and driving factors were analyzed first, and on this basis, the flash flood risk zoning was obtained. Results revealed that the flash flood disaster has the following characteristics： （ 1 ） dominated by heavy rainfall, the flash floods mainly distributed in the rainstorm areas of Longmen mountain with banding and group-occurring features; （2） the flash floods concentrated continuously in the scope of main earth- quake faults ; （3） the flash floods distributed in series or parallel characteristics ; （4） the blockage of river channel was serious because of collapses and landslides induced by the earthquake, and the critical precipitation of flash flood disasters decreased, resulting in the increase of scale and frequency of flash flood disasters and the exacerba- tion of the disaster. According to the rainstorm driving factor （the mean annual maximum precipitation in 1 hour） and earthquake driving factor （ distance from the earthquake fault）, the areas hit by flash flood disaster in the upper streams of Minjiang River can be divided into three zones： high risk area, moderate risk area and low risk area. The research results provide technical support for the monit6ring and early warning of flash flood disasters, proposing targeted flash flood disaster prevention system and reducing the loss of flash flood in mountain areas.