Use of LiDAR to Assist in Delineating Waters of the United States, Including Wetlands

Abstract : During preliminary delineations of an Ordinary High Water Mark (OHWM) boundary, LiDAR data or products may be used to view the OHWM signature across a project area and to estimate the height and location of two primary OHWM indicators: changes in vegetation and breaks in slope. At this time, most LiDAR data or products cannot detect changes in sediment texture. The point spacing, horizontal resolution, and vertical accuracy of the data or products determine if landscape features, such as the OHWM break in slope, can be measured with sufficient accuracy. All information gathered from LiDAR data or products should be verified in the field. During the preliminary, data-gathering stage of wetland delineations, LiDAR data and products may be used to view vegetative, topographic, and hydrologic patterns across a project area and to focus the investigation on transitional areas. They cannot provide evidence of hydrophytic vegetation or hydric soils. Although LiDAR intensity data may provide information on inundation extent, they contain no information regarding inundation frequency or duration and should not be used as a primary hydrology indicator. Intensity data collected during the growing season could be used as a secondary indicator of wetland hydrology. LiDAR data or products are not an adequate substitute for a field investigation.