Digital Terrain Model to Support Modeling of Lahars Originating on the West Side of Mount Rainier, Washington

This digital elevation model contains ground surface elevations for the valleys of rivers draining the west side of Mount Rainier, Washington. Elevations are mostly from the 1/9th arc-second (approximately 3 meter) resolution U.S. Geological Survey National Elevation Dataset (NED). The NED data were projected to the Universal Transverse Mercator Zone 10 coordinate system and mosaicked to form a single elevation grid of the study area. In the area of Alder Lake and La Grande Reservoir, along the Nisqually River, water surface elevations were replaced with approximations of lake-bed elevations. The bed elevation of Alder Lake is based mostly on bathymetry collected in 2010 and 2011 but is locally based on supplemental contours from the USGS 1:62,500 scale Ohop Valley quadrangle (1944), which was surveyed before the dam was built. Bed elevations of La Grande Reservoir are theoretical and were estimated by assuming parabolic cross sections along a thalweg whose elevation decreases linearly downstream. Along the Puyallup River in Orting, a new setback levee was constructed in 2014 and parts of the old levee were removed. The NED topography was modified using surveyed elevations along the new levee and the removed sections of the old levee were replaced with elevations based on the adjacent land surface as represented in a 2011 lidar-derived terrain model.