LANDSLIDE INVENTORY FOR THE WASHINGTON SIDE OF THE COLUMBIA RIVER GORGE: CLARK, SKAMANIA, AND KLICKITAT COUNTIES

The Washington Geological Survey produced a lidar-based landslide inventory for the Washington side of the Columbia River Gorge following a newly developed landslide inventory protocol. The inventory was created using 1-m high-resolution lidar and contains detailed landslide mapping in portions of three counties: Clark, Skamania, and Klickitat. The landslides were given 17 attributes, including a movement azimuth, estimated failure depth, and movement type as well as a unique ID number. The landslide inventory for the Gorge includes over 2100 landslide polygons, expanding upon previous mapping in the area. Landslide polygons cover 16 percent or 147 out of 897 square mile project area, with the largest landslide totaling nearly 9 square miles. Over half of the mapped landslides are of a complex movement type, meaning they incorporate more than one type of landslide movement (rotational slide, earthflow, etc.). Within the study area boundary lies a major state highway, six cities, and many popular recreation sites including a national scenic area.