Development of CSI index of convective rain for flash flood warning.

Abstract

A flash flood is a rapid flooding that occurs suddenly when it rains or after rain, due to the amount of rain intensity exceeding the capacity of the catchment or drainage system. Mostly, flash flood often occurs in steep terrain at upstream or foothill slope, also urban areas where have the high land-use changes. Especially nowadays, the rise of building and infrastructure that affects the exiting drainage system insufficient for current land use, which is the main reason for the ability of the drainage to be less. Therefore, the predicting rainy events, especially convective rain, is a challenge and a very useful one. In this study, CAPE and CIN values, which are the main parameters for convective rainfall of the hourly predicted rain from WRF-ROMS model, are used to analyze the correlation and calculate the convectional rainfall risk index (CSI). Also, the correlation between rainfall and flash flood events was analyzed. The result indicates that the high value of the index is effective for convectional rain warning. The index could then be applied to the Flash flood warning and decision support for the water management in accordance with the critical rainfall threshold.