COMPARATIVE LAHAR HAZARD MAPPING AT VOLCAN CITLALTÉPETL, MEXICO USING SRTM, ASTER AND DTED-1 DIGITAL TOPOGRAPHIC DATA

Abstract

In this study, we evaluated and compared the utility of spaceborne SRTM and ASTER DEMs with baseline DTED-1 “bald-earth” topography for mapping lahar inundation hazards from volcan Citlaltépetl, Mexico, a volcano which has had a history of producing debris flows of various extents. In particular, we tested the utility of these topographic datasets for resolving ancient valley-filling deposits exposed around the flanks of the volcano, for determining their magnitude using paleohydrologic methods and for forecasting their inundation limits in the future. We also use the three datasets as inputs to a GIS stream inundation flow model, LAHARZ, and compare the results. In general all three datasets, with spatial resolution of 90 m or better, were capable of resolving debris flow and lahar deposits at least 3 × 106 m 3 in volume or larger. Canopy- and slope-related height errors in the ASTER and SRTM DEMs limit their utility for measuring valley-filling cross-sectional area and deriving flow magnitude for the smallest deposits using a cross-sectional area to volume scaling equation. Height errors in the ASTER and SRTM DEMs also causes problems in resolving stream valley hydrography which controls lahar flow paths and stream valley morphology which controls lahar filling capacity. However, both of the two spaceborne DEM datasets are better than DTED-1 at resolving fine details in stream hydrography and erosional morphologies of volcaniclastics preserved in the valleys around the more humid, eastern flanks of the volcanic range.