Method for setting flash flood risk criteria in unmeasured areas using the relationship between flood damage risk occurrence characteristics according to topographical characteristics

Flood forecasting using ground-based rain gauges in urban and small mountainous basins is difficult due to the short lag time of the basin. It is important to secure prediction lead time for flood forecasting and prediction. For this reason, flood forecasting using rainfall radar and numerical forecasting has become an important tool for accurate and fast flash flood warning. This study aims to validate risk criteria equations for flash flood forecasting based on short-term forecasts and propose a standardized formula that incorporates topographical characteristics, enabling flood forecasting even in ungauged watersheds. The risk criteria can be set for any region with threshold rainfall durations between 30 and 180 min using the equations derived from the results of this study. The analysis results for past four years flood disasters showed high prediction accuracies (0.706 of POD) using these risk criteria equations. The results demonstrate that the flash flood risk criteria derived in this study provides meaningful information for strengthening flood preparedness and response in urban and small mountainous basins.