SPATIAL DISTRIBUTION OF LANDSLIDES IN PAONIA-HOTCHKISS AREA, COLORADO

Different types of mass movements are present in the Paonia-Hotchkiss area, among the most prominent are debris flows, landslides and rock falls. Landslides occur relatively frequently in this area and pose a risk to highway (Highway 139), railway (Union Pacific Railroad), and irrigation ditches. A method to identify landslides and their nature needs to be addressed to assess the potential risk of landslide hazard in this area. Thus, we developed a methodology to map landslides and study their relationship with geomorphic, geologic and engineering geologic parameters. Since the Paonia-Hotchkiss area is comprised of sedimentary and low-grade metamorphic rocks, the area is predisposed to downslope movement because of the weathered nature of these sediments. In addition, many of the slopes have been steepened as result of glaciations during the Quaternary. Landforms in the area include landslides, floodplains, and moraines. This study is the preliminary phase of the landslide hazard mapping in the Paoina to Hotchkiss area, which is comprised of parts of the North Fork Gunnison River watershed including Muddy Creek, Anthracite Creek, Deep Creek sub-watersheds, etc. The area is rugged mountain with slope ranging from gentle to very steep. North Fork Gunnison River is the major river of the area. Spatial distribution of the active landslides are mapped from aerial photographs and verified by field work. The size, shape, materials and other characteristics of the landslides are measured in the field. Slope, aspect, hillshade and drainage networks are developed from DEM. Lithology and geological structures are obtained from existing geological maps and landcover is derived from satellite images. GIS is used to map geology and landslides and to analyze the relationships of the landslides with landuse, slope, aspect, drainage, roads etc. Landslides are mainly distributed in and around Paonia, Somrest and Bowie. Moreover, landslides are found in the corridor of North Fork Gunnison River and its tributaries Muddy Creek, Deep Creek, Anthracite Creek, etc. Most of the landslides are found in medium slope, NE and SE facing slope and proximity to rivers and roads.