IMPACTS OF ROADWAY ENGINEERING ON THE SHORE OF YELLOWSTONE LAKE, YELLOWSTONE NATIONAL PARK

Along the western, northern, and northeastern shore of Yellowstone Lake (Yellowstone National Park), a primary road provides scenic views and visitor access to Yellowstone Lake. In several locations, shore protection structures (rip-rap and a seawall) were constructed to protect this roadway from erosion and maintain visitor access to the lake. However, reconnaissance photographs and results of preliminary shore surveys using precision laser surveying instruments suggest geomorphic differences indicative of enhanced erosion and shore degradation at engineered shore sites when compared to adjacent non-engineered shore segments. Among these morphological differences are 1) narrowing of dry beach width, 2) coarsening of beach texture, 3) complete loss of dry beach at low to normal lake levels, and 4) variable shore profiles. These results are consistent with commonly observed patterns of shore degradation associated with hard-stabilization in marine coastal settings, and provide evidence for differential responses of engineered and non-engineered lakeshore segments to shore zone physical processes at Yellowstone Lake. Ironically, then, roadway engineering intended to provide visitor access to the Yellowstone Lake shores may ultimately eliminate visitor-usable shore sites. During the next few years, monitoring and repeat surveys of engineered and non-engineered shore segments will provide insight into the magnitude of differential shore responses and may inform long-term park planning, management, and resource conservation in order to preserve the quality of the lakeshore environment and the quality of visitor experiences at Yellowstone Lake.