STATISTICAL AND REMOTE SENSING BASED APPROACH TO DETERMINE DEBRIS FLOWS TRIGGERING FACTORS

Debris flows represent a significant ecosystem disturbance, particularly in Jazan Mountains in Saudi Arabia. The area is subjected to intense precipitation levels related to Indian monsoons and high relief (up to 2.5 km a.m.s/l). We were able to characterize the spatial conditions that have controlled the occurrence of debris flows events in the area due to the advancement of remote sensing and geographic information systems. We extracted terrain characteristics in the area from remote sensing datasets, and used them as proxies to the different debris flows triggering factors. The remote sensing based parameters enable us to construct a weighted model that is calibrated against field based observations. The extracted criteria that enable us to control slope instability for shallow debris flows are: slope angle, elevation, topographic wetness index (TWI), stream power index (SPI), convergence index (CI), aspect, soil roughness, normalized difference vegetation index (NDVI), flow accumulation index, and manmade feature distribution.