LANDSLIDE RISK REDUCTION THROUGH DETAILED LANDSLIDE INVENTORIES AND STAKEHOLDER-DRIVEN COLLABORATION IN WASCO AND GRANT COUNTY, OREGON

The Oregon Department of Geology and Mineral Industries (DOGAMI) recently completed landslide inventory mapping of 600 square miles (mi2) of Wasco County and 280 mi2 in Grant County, Oregon. The mapping identified 4,246 landslide features, where each landslide is characterized by 25 unique attributes, including landslide movement type (e.g., rotational rockslide, debris flow or rockfall) estimated failure depth, and associated geologic unit. Mapping in Wasco and Grant County was completed using well established methods and protocols for developing landslide inventories (Burns and Madin, 2009), using 3 ft-resolution lidar, orthophotos, and field validation, with all mapping undertaken at 1:8000 scale. Once published, the landslide inventory will be publicly available via webmap or downloadable geodatabase and will be presented to community stakeholders. In collaboration with the Oregon Department of Land Conservation and Development, DOGAMI staff held a series of meetings with a variety of stakeholders in both counties to create a list of risk reduction strategies that could be implemented to mitigate their community’s risk from landslides. Examples of such actions are: adopting updated landslide inventory maps in land use codes, including a geotechnical or geological engineering assessment in the planning or permitting process, and connecting the public with landslide data and information. Key stakeholders who participated include city managers, engineers, permitting specialists and planners. In this poster, we present the final landslide inventory maps defined for Wasco and Grant county, Oregon, as well as the stakeholder-driven risk reduction action list, and summary of our collaborative approach toward landslide risk reduction in both counties.