GIS modeling of the geomorphic parameters on avalanche pathways: Telluride, Colorado

Abstract

Often the focus of a site evaluation is to determine and evaluate the potential occurrence of natural hazards resulting from geomorphic processes. This focus becomes important in mountain environments such as Colorado where the State Legislature has mandated that an appraisal of the potential hazards of a site must be completed before development permits can be issued. One such area is Telluride, which has become a major recreational site with real estate development expanding into areas with unknown potential for hazard occurrence. Interpretation of geomorphic deposits indicates that the Telluride area is prone to various hazards(avalanches, landslides, other types of mass wasting, and flooding). Mapping and evaluating these complex geomorphic processes can be facilitated with a Geographic Information System (GIS). Understanding of and access to a GIS is one of the best "tools" a geographer can possess for evaluating the potential hazards of a site. A GIS integrates multiple types of complex data which have been georeferenced and manipulated by a computer. Various types of data, including a DEM at 1:24,000, surficial geology, geomorphology, avalanche paths, and structure were scanned and vectorized into the computer for this thesis.The GIS enabled a focus on the extrinsic controls of the avalanche paths and the results were used to produce an avalanche hazard map. It was found that 65 percent of the starting zones occurred on slopes between 30 and 45 degrees; 51 percent of the paths are within 100 m of the 3500 m treeline; and the volcanic conglomerate of the San Juan Formation contains the largest frequency of avalanche starting zones. Through cartographic modeling in the GIS environment an avalanche initiation hazard map of the area was produced in which the potential occurrence of avalanches was mapped as high, medium, and low.