Quantitative high-resolution coastal elevation information is required to build integrated topobathymetric elevation models, inventory wetland and agricultural land resources, and identify inundation hazard zones caused by floods, hurricanes, and sea-level rise. Many applications of geospatial data in coastal environments require detailed knowledge of near-shore topography and bathymetry, as physical processes in the coastal environments are controlled by the geomorphology of both “over-the-land” topography and “underwater” bathymetry. Light detection and ranging (lidar) enables the rapid collection of accurate elevation data over large areas. During the last decade, airborne laser altimetry has been widely applied to map coastal geomorphology, leading to improved knowledge of coastal geomorphic processes.
The Coastal National Elevation Database (CoNED) applications project, supported by the USGS Coastal and Marine Geology Program (CMGP), is constructing high-resolution integrated topobathymetric elevation models from disparate lidar and acoustic bathymetric datasets aligned both vertically and horizontally to common reference systems. Topobathymetric digital elevation models (TBDEMs) are merged renderings of both topography (land elevation) and bathymetry (water depth). Topobathymetric models provide a required seamless elevation product for several science application studies such as shoreline delineation, coastal inundation mapping, sediment-transport, sea-level rise, storm surge models, tsunami impact assessment, and analysis of the impact of various climate change scenarios on coastal regions.
One high visibility application of these data is the USGS Hurricane Sandy synthesis project. Hurricane Sandy severely impacted the eastern United States coast, altering the topography, bathymetry, and ecosystems of this heavily populated region. The USGS is developing high-resolution (1-m) three-dimensional (3D) topobathymetric models from Cape Cod to the Outer Banks in North Carolina that integrate dozens of high-resolution lidar and bathymetric surveys acquired by numerous sources. Pre- and post-Hurricane Sandy remote sensing lidar data are being used to construct wetland extent geospatial products that will enable predictive sediment-transport flow modeling across wetlands in the Forsythe National Wildlife Refuge in New Jersey.
Extreme storm events like Hurricane Sandy and other natural hazards can impact the spatial distribution of land and water in coastal wetlands and change the capacity of the ecosystem to provide services such as water-quality enhancement, protection of populated areas from storm surge flooding, and habitat for fish, shellfish, and other wildlife. TBDEMs will help inform the nature of these changes.
Coastal National Elevation Database—wetland extent mapping research.