Search

A model for the analysis of topographic influence on shallow landslide initiation is applied to an experimental mountain basin where high-resolution digital elevation data are available: the Cordon catchment (5 km2) located in northern Italy. The model delineates those areas most prone to shallow landsliding due to surface topographic effects on hydrologic response. The model is composed of two parts: a steady-state model for shallow sub-surface runoff and an infinite-slope Coulomb failure model which assumes that the soil is cohesionless at failure. An inventory of landslide scars is used to document sites of instability and to provide a test of model performance by comparing observed landslide locations with model predictions. The model reproduces the observed distribution of landslide locations in a consistent way, although spatial variations in soil strength and transmissivity, which are not accounted for in the model, influence specific distribution of landslide areas within regions of similar topographic control. [ABSTRACT FROM AUTHOR]

The use of digital elevation models (DEMs) allows the automatic derivation of channel networks and the quantitative description of the geomorphic characteristics of basins. A common method of channel network extraction from DEM data is based on the specification of a threshold area (A{sub}t{end}) that is the minimum support area required to drain to a point for a channel to form. Usually, an arbitrary constantthreshold area value is chosen for channel network extraction. In this study the effects of threshold area selection, both on the morphometric and scaling properties (such as drainage density, total channellength, Horton laws and fractal dimension) of a channel network and the associated hydrological response function are analysed. The response is obtained following the geomorphological instantaneous unit hydrograph theory. Two different probabilistic models are used. They both relate the characteristic response function of the basin to its DEMdata derived networks: one is derived assuming a Strahler stream ordering system and the other is obtained by averaging a flow equation with respect to the network structure (described by the width function). Applications are shown for three mountainous basins in the ItalianAlps. A sensitivity analysis is performed to study the influence of the variability of morphometric properties, with respect to A{sub}t{end}, on the hydrological response obtained. It is shown that the model based on the width function is able to reduce the effects of this variability on the simulated response. [ABSTRACT FROM AUTHOR]