VALIDATION OF SPOT-5 SATELLITE IMAGERY FOR GEOLOGICAL HAZARD IDENTIFICATION AND RISK ASSESSMENT FOR LANDSLIDES , MUD AND DEBRIS FLOWS IN MATAGALPA , NICARAGUA

This analysis addresses the suitability and potential for the use of high-resolution SPOT-5 remote imagery for geological hazard identification and risk assessment in Matagalpa, Nicaragua. SPOT-5 products are complementary tools in the process of risk analysis and in combination with digital elevation models (DEMs) are particularly helpful for determining large, kilometer-sized hazardous phenomena for watersheds. At Matagalpa, a pseudo-color 2.5 m SPOT-5 image draped over a DEM for 3D simulation is tailored for mapping landslide scarps and recent debris flow deposits at scales up to 1:25’000, but is inappropriate for identifying mud flow events. In contrast, the input of SPOT-5 derived products to hazard susceptibility mapping is limited, since among the prime factors controlling terrain instability (slope, geology, hydrography), only information about geological lineaments can be recovered. A few second-order risk factors, such as barren soils and deforested areas can be extrapolated from SPOT-5 land cover and change detection maps. For vulnerability issues, SPOT-5 images are a relevant source of spatial information on threatened elements (settlements, road infrastructure), if there are neither quality, nor current maps of the area available.