Geologic maps are useful in identifying areas that may be affected by post-wildfire debris flows. Land-use planners use these maps to identify potential hazards in areas that are proposed for development and to develop mitigation strategies. The maps can also focus post-wildfire emergency planning on the areas with the highest likelihood of debris flows. It is cheaper to avoid or mitigate problems than to repair damage.
Damaging landslides occur even in vertically challenged states like Kansas (Fig. 1). It is important to be able to delineate landslide hazard areas in order to develop appropriate land-use plans. In Leavenworth County, Kansas, geologic maps combined with maps of landslide features and slope steepness were used to predict landslide hazards and guide land management.
Wildfires, such as the Missionary Ridge fire that burned for more than a month in 2002 near Durango, Colorado (Fig. 1), and their aftermath can cause subsequent property and environmental damage. Many areas denuded by the fire are now susceptible to rapid erosion during heavy precipitation with resulting debris flows, or mudslides.
U.S Highway 85 and ND Highway 22, along with numerous county roads, buildings, pipelines, and power lines, have been constructed over existing landslides in the Little Missouri Badlands of western North Dakota. Since 1980, the repair and rerouting of damaged sections of highways in this area have cost taxpayers more than $5 million (Fig 1). In one instance, a one-mile segment of U.S. Highway 85 was rerouted from one area of landslides into another. Better understanding of landslide hazards is needed in this area.
Landslides are also known as mass wasting and are characterized by the downward movement of rock caused by gravity. Landslides typically occur when a slope becomes unstable. Rock falls, debris flows, slumps, lateral spread, and creep are all types of landslides. Landslides can cause considerable damage.
This deep-seated landslide study was designed to serve the dual purposes of compiling an inventory of deep-seated landslides for a portion of the Olympic Peninsula and providing geological information for the state geologic map (Schuster, 1996). The results of the study are intended to provide information for land managers, planners, and scientists making land-use decisions regarding natural resources and wildlife habitat.
In response to the Nisqually earthquake of 2001, DGER was awarded a grant by the Federal Emergency Management Agency and Washington Emergency Management Division to develop two types of earthquake hazard maps for every county in the state—liquefaction susceptibility maps, which outline areas where water-saturated sandy soil loses strength during earthquake shaking, and NEHRP (National Earthquake Hazards Reduction Program) site class maps, which outline areas where soils amplify ground shaking. The maps will be used by state and local governments to update existing hazard mitigation plans and to delineate geologically hazardous areas under the Growth Management Act.
Landslides in western Washington cause millions of dollars in damage each year. Accurate and precise remote sensing techniques are a necessary first step in creating useful landslide inventories for future land use planning and engineering mitigation decisions. Both aerial photos and LIDAR (LIght Distance and Ranging) imagery were evaluated and compared on the basis of the accuracy of landslide location and the precision of landslide boundary definition for an eight-kilometer stretch of heavily forested coast along Hood Canal, Kitsap County, Washington, an area which is characterized by numerous slides occurring in Pleistocene glacial and non-glacial sediments. Independent landslide inventories were developed from each remote sensing dataset and were followed by field observations of approximately half of the identified slides.