A physics-based model to derive rainfall intensity-duration threshold for debris flow

Abstract

A statistical method to establish an intensity-duration curve (I-D curve) for debris flows is highly dependent on a large amount of debris flows and rainfall events and is impossible for a gully lacking observation data. To overcome this limitation, a physics-based model to derive the I-D curve is presented. In this new model, the density of the debris flow is chosen as the key parameter, based on which, the rainfall intensity and duration necessary for fitting I-D curve are obtained. The physical model is validated in Jiangjia Gully, a typical debris flow valley with several debris flows each year. A series of I-D curves under the conditions of different antecedent rainfalls were fitted. These derived curves are similar to the shape of the curve from the statistical method, but having upper and lower boundary lines related to the necessary conditions for the occurrence of debris flows. The precision of the new model is identified as about 80.5% using 63 collected rainfalls in Jiangjia Gully in Yunan province, China. This value is 27.7% higher than the curve fitted through the statistical method. This new physical model is capable of improving the deficiency of the statistical method and has great application potential for predicting debris flows.