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Kittitas County, WA <br />s 174.02.470 KITTITAS COUNTY CODE 5 t7 A.02.470 <br />S 17A.02.470. Landslide hazard areas. <br />"Landslide hazard areas't are areas potentially subject to landslides based on a combination of geologic, <br />topographic, and hydrologic factors. They include any areas susceptible because of any combination of <br />bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors. A slope is delineated by <br />establishing its toe and top and measured by averaging the inclination over at least ten (10) feet ofvertical <br />relief. Potential landslide hazard areas include but are not limited to the following areas: <br />1. Areas designated as quatemary slumps, earth-flows, mudflows, or landslides on maps published <br />by the U.S. Geological Survey or Washington State Department of Natural Resources. <br />2. Areas with all three (3) of the following characteristics: <br />a. Slopes steeper than fifteen percent (15%); <br />b. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a <br />relatively impermeable sediment or bedrock; and <br />c. Springs or groundwater seepage. <br />3. Areas that have shown movement and/or are underlain or covered by mass wastage debris; <br />4. Slopes that are parallel or sub-parallel to planes of weakness (which may include but not <br />be limited to bedding planes, soft clay layers, joint systems, and fault planes) in subsurface <br />materials; <br />5. Slopes having gradients steeper than eighty percent (80%) subject to rock fall during seismic <br />shaking; <br />6. Areas that show evidence of, or are at risk from snow avalanches; and <br />7 . Any area with a slope of forty percent (40%) or steeper and with a vertical relief of ten (10) or <br />more feet except areas composed of competent bedrock. <br />8. Potentially unstable slopes resulting from river erosion or undercutting. <br />9. Areas that show past sloughing or calving of sediment or rocks resulting in a steep slope that is <br />poorly vegetated. <br />10. Deep-seated landslide areas characterized by one or more of the following features, which may <br />be evident in aerial images, topographic maps, LiDAR imagery or on the ground: <br />a. scalloped ridge crests at the top ofthe slope, <br />b. crescent shaped depressions, <br />c. head scarps, <br />d. side scarps, <br />e. ponds or sag areas on mid slopes, <br />f. benches and scarps on mid slope areas, <br />g. hummocky ground, <br />Downloaded from https://ecode360.com/Kl6857 on 2025-05-15