Analysis of topographic and climatic control on rainfall-triggered shallow landsliding using a quasi-dynamic wetness index

A model for the prediction of both topographic and climatic control on shallow landslide initiation processes in hilly mountainous terrain is proposed. The model develops upon a theory for coupled shallow subsurface flow and landsliding of the soil mantle previously proposed by Montgomery and Dietrich [Water Resour. Res. 30 (1994) 1153]. The model uses a 'quasi-dynamic' wetness index to predict the spatial distribution of soil saturation in response to a rainfall of specified duration. The rainfall predicted to cause instability in each topographic element is characterised by duration and frequency of occurrence. The incorporation of a rainfall frequency-duration relationship into assessment of landslide hazard provides a practical way to include climate information into estimation of the relative potential for shallow landsliding. The model is applied to a mountain experimental basin where high-resolution digital elevation data are available: the Cordon catchment (5 km2), in north-eas...