LIDAR BASED LANDSLIDE INVENTORY AND SUSCEPTIBILITY MAPPING FOR THE PANTHER CREEK WATERSHED, COAST RANGE, OREGON

LIDAR (Light Detection and Ranging) elevation data was collected in the Panther Creek Watershed in December and September 2007 and March 2009. LIDAR derived images from the March 2009 dataset were used to map pre-historic, historic, and active landslides in the area. Each mapped landslide was characterized as to type of movement, head scarp height, slope, failure depth, relative age, and direction. The LIDAR bare earth digital elevation models (DEMs) were subtracted from each other resulting in a differential dataset to examine changes in ground elevation. Areas with significant elevation changes were identified as potentially active landslides. 29 landslides are considered active based upon differential LIDAR and field observations. A total of 140 landslides were mapped and then field checked in the study area. Deep-seated earth flows and rotational landslides are the most common slope processes with a mean estimated pre-failure slope of 27°. For this project deep-seated landslides are defined by a failure depth greater than 4.5 meters. A historic record of landslide activity in the study area was created using aerial photography. Mapping landslides on serial aerial photography provided accurate dates of movement for several landslides. A shallow-seated landslide susceptibility map was generated using the landslide inventory, calculations of factor of safety, and buffers. The results of the susceptibility map indicate that 29% of the study area is highly susceptible to landsliding and 54% is moderately susceptible. Due to the high number of deep-seated landslides, a deep-seated susceptibility map was also created. The results of this study include a detailed landslide inventory including pre-historic, historic, and active landslides and a set of susceptibility maps identifying areas of potential future landslides.