Applying a GIS slope-stability model to site-specific landslide prevention in Honduras

ABSTRACT:

Conventional output of an environmental landslide model is some form of a distributed hazard index. Viability of these models has proven to be strong in tested environments, and this has encouraged modelers to apply landslide hazard models to tropical regions that generally lack advanced information systems. For steep-land farmers in the tropics, however, information on relative landslide hazard is useful but not sufficient, as knowledge of primary causes of instability is needed to develop management practices for sustained use of landslide-prone lands. Stability Index Mapping (SINMAP) is a physical slope-stability model in which relative hazard predictions are primarily governed by local slope gradient (α) and relative wetness (W). This model was applied to an agricultural region of Honduras that suffered extensive landslide damage during Hurricane Mitch, and its stability predictions were empiricaliy evaluated. Zones of predicted instability were subsequently categorized according to α, derived from the Digital Elevation Model, and W, based on steady-state hydrology for hurricane conditions. W and α varied in a soil-specific and site-specific manner, indicating that site-specific management strategies are required for slope stabilization in the study area. Knowledge of α*W in potentially unstable zones allows for informed stability management practices, improving the utility of the hazard model for communities that contend with landslide risk.