LiDAR-Based Geomorphic Mapping in Forested Landscapes: Using trees to your advantage

The method was developed to study valley bottom evolution in response to debris flows in catchments flanking Mount Rainier. With this technique, we are able to: 1) map geomorphic features of differing relative age; 2) provide a rational basis for designing a dendrogeomorphic sampling strategy based on identifying abandoned channels with adjacent old-growth trees that record evidence of debris flow disturbance; and 3) map extents of individual recent debris flow events. The LiDAR data used for this study was collected in 2007-2008, in part, as a response to a storm event in 2006 that unleashed major debris flows from multiple drainage basins. The DCM/DTM method clearly differentiates thinned stands where 2006 debris flows spilled from channels into adjacent forests. Examples from the Kautz Creek drainage basin reveal recent events, known historical events, as well as previously unrecognized pre-archival debris flow events. This method provides a simple, first-order tool to develop high-resolution chronologies of geomorphic surface evolution in areas with minimal anthropogenic disturbance