USING LIDAR REMOTE SENSING TO MAP KARST TOPOGRAPHY IN A TEMPERATE RAIN FOREST - CASE STUDY: TONGASS NATIONAL FOREST, SOUTHEASTERN ALASKA

The Tongass National Forest is situated in Southeastern Alaska within a rugged and remote landscape and mostly temperate rain forest. A portion of the Tongass is underlain by carbonate bedrock with relatively well developed karst topography that is protected under the Federal Cave Protection Act of 1988. The Tongass has been using Light Detection and Ranging (LiDAR) remote sensing to support environmental analyses related to timber management and road construction. URS Corporation has managed on the behalf of the Tongass the collection and analysis of the LiDAR data, using Geographic Information System (GIS) software, for approximately 1500 square miles of the temperate rain forest, a portion of which is underlain by carbonates. The LiDAR-derived data have been demonstrated to be useful in completing pre-field mapping of the karst landscapes to support the environmental analyses by generating relatively detailed digital elevation models (DEMs) of the "bald earth". Depression contours and hydrologic "sinks" were also generated using different software models. The GIS-based data were confirmed in the field. The LiDAR data have aided in karst resource inventories and karst vulnerability classification. The maps generated from the LiDAR data were found to be instrumental in better understanding the landscape for a variety of disciplines involved in environmental analyses with significantly less effort and improved resolution than pre-existing methods.