BRADD Landslide Susceptibility

Data Source: KYEM 2018 Hazard Mitigation Plan - Landslides A statewide landslide susceptibility model was developed in ArcGIS using two map layers: geology and slope. The geology and slope maps (raster images) were reclassified based on a matrix of weighted scores that were assigned to particular geologic formations and ranges of slope values (Table 2-5). The weighted score for slope doubled with each increasing slope range. The weighted score for the geology ranged from 10 to 40 depending on the rock type. Using the ArcGIS Weighted Sum tool, the newly reclassified values of both raster map layers were multiplied by an assigned weight and then values for both layers were added together (Eq. 2-1). In order to have slope be a greater influence on the susceptibility model, a 70 percent weight was assigned for slope and a 30 percent weight was assigned for geology. Eq. 2-1 (geology reclass value × 0.30) + (slope reclass value × 0.70) = landslide susceptibility value Using the summed cell values from the two layers, landslide susceptibility was manually classified into low, moderate, and high categories (Fig. 2-8). Classification was made by visually inspecting the map and by determining the distribution of existing landslides cataloged in the Kentucky Geological Survey inventory.<o:p></o:p>