USFS Inundation Mapping and Preparation of EAPs - Regions 1, 2, 3 and 4 — Natural Resources Conservation Service (NRCS)

Tetra Tech was the prime contractor for the NRCS, to provide a high definition LiDAR model to support an inundation mapping study over two areas in the vicinity of Smoot, Wyoming. During the acquisition campaign, the aircraft covered the 8,300 acres of the project area to collect an airborne LiDAR point cloud with a density exceeding 8 points/m2. A ground control survey campaign was also conducted to assess the absolute accuracy of the LiDAR dataset.

The LiDAR point cloud was classified in order to provide accurate models of the topography. In a second processing phase, as the final digital terrain models will be used for an inundation study. Hydro-enforcing breaklines were collected to simulate the natural water flow under bridges and culverts. The flat water surfaces were also collected in order to make sure that they are well represented in the various derived end products.

Based on the classified LiDAR point cloud, the flattening breaklines and the hydro enforcing breaklines, digital elevation grids were generated with a resolution of 50 centimeters. Contours with a 25-centimeter contour interval were also derived from the same input. Finally, as no imagery was collected for this project, LiDAR intensity images with a 1 meter resolution were also provided.

The airborne acquisition was completed by Aero-Graphics, Inc., the ground survey campaign was undertaken by the U.S. Forest Service Intermountain Regional Office, and the data processing was done by the Tetra Tech Geomatic Technologies Group in Lafayette.


Renee Walmsley

(303) 448-7446