DATING OF LANDSLIDES IN CLACKAMAS COUNTY, OREGON, USING LIDAR-BASED IMAGING AND GIS ROUGHNESS MODELING

The use of Light Detection and Ranging (LiDAR) has become widely accepted in the field of geology to remotely study regional topography. The point data from LiDAR can be used to create very accurate digital elevation models (DEM). Using the LiDAR DEMs available, fluvial terraces and landslides along the Clackamas River in northwest Oregon can be identified. A roughness model will also be applied to the DEMs of the study area to more objectively identify the landslides.

Many of the fluvial terraces along the Clackamas River have been dated to be Holocene in age. The ages of these terraces can be used in conjunction with analysis of soil profiles within landslides to determine the relative age of landslides within these terraces. The relative age of landslides along the Clackamas River can be determined by dating the age of the soils that have developed on these landslides and constrained by the known age of the terraces. Currently, the protocol used for identifying and dating landslides for susceptibility maps is done using a subjective dating technique. I hypothesize that the use of a roughness model and LiDAR DEMs can be combined to objectively date landslides.