Flash flood vulnerability assessment for small catchments with a material flow approach

Flash flood often causes serious losses in small catchments of China. Nevertheless, the flash flood vulnerability assessment is relatively limited in China. This paper presented a material flow assessment framework to evaluate the flash flood vulnerability for small catchments in Wuzhishan County of Hainan province, China. The framework was developed into three parts: selection of typical villages and small catchments, calculation of exposure, sensitivity and adaptive capacity with material flow analysis, and multiple evaluation of vulnerability with the proposed material flow indices. In this framework, all material flows of exposure, sensitivity, and adaptive capacity were measured by water’s mass. Then, the relationship between the three elements of vulnerability was established through material flow indices. Results of the three elements of vulnerability and four material flow indices in each small catchment were exhibited via GIS. The evaluation results suggested that catchments with lower exposure, sensitivity, and adaptive capacity did not necessarily lead to lower vulnerability, as the inherent relationship among them might aggravate the vulnerability of catchments to flash flood. Some suggestions were put forward for the prevention of flash flood based on the vulnerability assessment. Finally, the advantages and disadvantages of the approach were discussed.