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

摘要

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.