Implications of Different Digital Elevation Models and Preprocessing Techniques to Delineate Debris Flow Inundation Hazard Zones in El Salvador

Landslides caused by heavy rains on steep, volcanic slopes pose a persistent threat in El Salvador. Particularly for volcanic debris flows (lahars), limitations in digital elevation model (DEM) spatial resolution, acquisition date of the data, and hydrological preprocessing techniques can contribute to inaccurate hazard-zone delineations. This chapter investigates these limitations to determine which combination of methods most closely agrees with observed lahar events on San Vicente volcano. The hydrologic preprocessing techniques employed affected the extent of the debris-flow zones only under those modeled using global DEMs. For more precise lahar mapping, lidar-derived DEMs are often preferred because they can resolve different levels of materials such as vegetation and bare earth and can capture fine-scale anthropogenic and natural topographic features that can push a debris flow one in any given direction. The limited availability of such lidar-based datasets is often a challenge for landslide hazard modeling, particularly in Central America.