Calculation of rainfall thresholds for debris flow prediction

Abstract

Due to the fact that debris flow movements, commonly known as "huaycos," represent a potential threat worldwide, especially in Peru, it is necessary to analyze and study this hazard, as well as the ability to forecast these movements. Therefore, the objective of this research was to determine the precipitation thresholds that trigger debris flow movements in the Rosayoc/Batán ravine, in order to contribute to Disaster Risk Management (DRM). As a means of processing spatial data, this study used an approach that combines Geographic Information Systems (GIS), remote sensing, and satellite image analysis. Additionally, through the hierarchical analysis process, the most susceptible areas to debris flow in the Rosayoc/Batán ravine were evaluated and determined. In conclusion, the True Skill Statistic (TSS) of the thresholds was calculated through calibration and validation. This indicates that the model's ability to predict future outcomes was evaluated. Additionally, through the analysis and evaluation of hazard levels for debris flow movements using the hierarchical analysis process (CENEPRED 2014), it was established that the lower part has very high and high levels of hazard, the middle part has high and medium levels, and the upper part has a high level of hazard. Furthermore, these levels have the highest predominance of area in each part of the ravine. Moreover, hazard maps were also created for debris flow movements triggered by the maximum 24-hour precipitation and the critical threshold of accumulated rainfall (LA1) over 18 days, based on the maximum depths and velocities generated by the debris flow.