Peak Flood Discharge from a Landslide Dam Outburst

Abstract

A rapid method for estimating the peak discharge from a breached landslide dam is developed from an analysis of 42 outburst floods. Systematic classification of the river blockages based on the landslide type, its material composition, and its travel distance is used to assess the erodibility of a dam. The blockage erodibility, along with the impoundment’s characteristics, controls the size (height and width) of a breach and the speed at which it forms, which determines the peak discharge. Three categories or types of landslide dams are identified to quantify their relative erodibility. A regression equation is developed to predict an outburst flood peak discharge based on the blockage type, the dam height, and the volume of impounded water at the time of breaching. Prediction limits are also calculated, which provide a sound statistical assessment of the possible peak outflow range. With the potential consequence known, the downstream population’s orderly evacuation can be carried out when a landslide dam failure is approaching.