Coastal Changes and Impacts

Hydrologic-Enforcement of Lidar DEMs

Hydrologic connectivity of light detection and ranging (lidar)-derived elevation data is critical for coastal hydrologic modeling applications. However, unless hydrologically-enforced, raised structures (i.e. bridges, roads overlaying culverts) can block overland flow to coastal waters. Because highly detailed lidar-derived elevation surfaces include features such as bridge decks and road fill overlying culverts, artificially pooled depressions that form upstream of drainage structures impede down slope flow. Hydrologic-enforcement enables hydrologic models to simulate flow under bridges and through culverts by modifying the elevations of artificial impediments.

Hydrologically-enforced lidar-derived elevation data are an essential base layer for complex modeling of surface water flow. The USGS Coastal and Marine Geology Program is integrating hydrologically-enforced lidar-derived land elevation and lidar-derived bathymetry (water depth) to enhance storm surge modeling in vulnerable coastal zones. Hydrologic-enforcement of topobathymetric surfaces has rarely been employed to achieve hydrologic connectivity.

Additional information on hydrologic-enforcement is available at http://pubs.usgs.gov/fs/2014/3051/ and http://pubs.er.usgs.gov/publication/sir20105059.

Hydrologic-Enforcement of Lidar DEMs
Surfaces showing topographic elevation surface with road fill over a culvert (left image) and hydrologic elevation surface with hydrologic-enforcement at the drainage structure (culvert) location. U.S. Geological Survey image created by Sandra Poppenga.

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