Optimization approach for determining rainfall duration-intensity thresholds for debris flow forecasting

Debris flow is a natural hazard typically triggered by heavy rainfall. Previous research aimed at forecasting the occurrence of debris flows have led to the development of several rainfall duration-intensity thresholds for different areas using the second-percentile method that allows a missed-alarm probability of up to 2%, while disregarding the occurrence of false alarms. The current study aims to develop rainfall duration-intensity thresholds for debris flow forecasting taking into account both missed alarms and false alarms. Specifically, the new optimization approach seeks to determine the optimal duration-intensity threshold associated with the lowest missed- and false-alarm probabilities combined. In addition to the methodology, a case study is presented to show that the new optimization approach is feasible for determining rainfall duration-intensity thresholds in debris flow forecasting, and is more efficient than the method currently in use, which is associated with a higher probability of missed and false alarms combined.