ASSESSMENT OF HUMAN RISKS POSED BY DEADLY DEBRIS FLOW IN THE WENCHUAN EARTHQUAKE AREA

Abstract

Prolonged rainstorms had triggered several large-scale debris flows along Provincial Road 303 near
the epicenter of the 2008 Wenchuan earthquake. A lot of concrete-aggregate plants distributed along this road
were buried by the runout debris, leading to a large number of fatalities. A Quantitative Risk Assessment (QRA)
methodology is being developed for debris flows induced by various rainfall scenarios. QRA for these debris flow
hazards is of significance to determine the probability distribution, consequence and human risk profile arising
from these disasters. With the aid of Geographic Information System (GIS) platform, a potential channelized debris
flow catchment in the study area is identified based on remote sensing images and field study. Rainfall intensityduration thresholds for the local channelized debris flows are used to determine the occurrence probability under
six rainfall scenarios for the purpose of hazard analysis. Subsequently, human losses of debris flow are assessed
by considering the variations of rainfall events, and the final human risks can be obtained using a general risk
model. Finally, the societal human risks are obtained, which provide a benchmark for studying the long-term
human risks of these potential debris flows and engineering decision in the perspective of mining manufacture.