GEOMORPHOLOGY OF NON-ENGINEERED VERSUS ENGINEERED SHORES OF YELLOWSTONE LAKE, YELLOWSTONE NATIONAL PARK

Geomorphic differences between non-engineered and engineered segments of the Yellowstone Lake shore were quantified from shore profiles acquired using precision laser surveying equipment, nearshore high-resolution bathymetry acquired from dual frequency echo sounder data, and beach texture derived from sediment grain size analyses. Results from an initial survey conducted in July-August 2005 established that there are significant geomorphic differences between non-engineered and engineered shore segments of Yellowstone Lake. Visual observations and surveyed shore profiles show non-engineered shore segments display relatively wide beaches composed of sand to fine gravel with gently sloping, concave-up shore profiles. Engineered shores typically display narrow or non-existent beaches, coarse sediment texture (gravel to coarse gravel), with steep upper (landward) profiles associated with shore protection structures and flat lower (offshore) profiles. Thus, engineered segments of the Yellowstone Lake shore exhibit morphological features similar to those associated with hard stabilization of marine and Great Lakes coastal settings and are suggestive of enhanced erosion and shore degradation at engineered shore sites when compared to adjacent non-engineered shore segments. Ongoing monitoring and repeat annual surveys of study sites will record evolution of shore segments in response to shore armoring, including evolution of the recently engineered shore of Mary Bay (northeast shore of Yellowstone Lake) while providing enhanced understanding of shore zone processes at Yellowstone Lake. Results from this study may also aid in developing alternative strategies for protecting lakeside infrastructure while at the same time conserving lakeshore resources and preserving the quality of visitor experiences at Yellowstone Lake.