A 10-min rainfall prediction model for debris flows triggered by a runoff induced mechanism

Debris flows are triggered every year in the Jiangjia Gully, Yunnan Province, China. High-intensity short duration rainfall was the main triggering factor for these gully type debris flows which are triggered by a runoff induced mechanism. The 10-min rainfall intensity is considered as the trigger. A revised prediction model with factors related to hydrology (rainfall) is introduced for this kind of gully type debris flows and applied to the Jiangjia Gully. A 10-min rainfall coefficient intensity is proposed based on the observational data of Jiangjia Gully, and a minimum 10-min rainfall intensity for triggering debris flow is presented. The Jiangjia data were used also to assess critical boundaries between three probability classes of debris flow initiation. The model was successfully validated in debris flow gullies with the same initiation mechanism in other areas of southwest China. The generic character of the model is explained by the fact that its factors are partly based on the initiation mechanisms and not only on the statistical analyses of a unique variety of local factors. The research provides a new way to predict the occurrence of debris flows initiated by a runoff induced mechanism.