Contrary to common myth, half of the City of New Orleans is either at or above sea level.1 Portions of the Greater New Orleans area are low lying, with elevations spanning from below sea level to 205 feet in St. Tammany Parish. Subsidence has lead to portions of the region being below sea level. The sinking is attributed to swamps drained to accommodate population growth earlier in New Orleans’ history as well as soft soil conditions. Elevation data is obtained obtained through optical remote sensing technology, known as Light Detection and Ranging (LIDAR). LIDAR allows for the measurements of distance. The State of Louisiana provides state-wide LIDAR data. Data is publicly available for download at http://atlas.lsu.edu/lidar. National Geodetic Survey (NGS) and the Louisiana Spatial Reference Center also provide information on bench mark elevations and additional Global Positioning System (GPS) sites in coastal Louisiana for the area south of Interstate 10. The GEOID03 model for this area has been updated. This information should be incorporated into all recent, current, or planned surveying efforts in this region which are elevation sensitive.
The Federal Emergency Management Agency (FEMA) has released preliminary flood hazard maps for all Louisiana coastal parishes through the Louisiana Mapping Project (LaMP). These maps, known as Digital Flood Insurance Rate Maps (DFIRMs) provide FEMA’s most current picture of coastal Louisiana Flood risks. In five parishes (Jefferson, Orleans, Plaquemines, St. Bernard, and St. Tammany parishes) where major levees are being built, maps will be updated upon the completion of levee construction. Additional Geographic Information Systems (GIS) data pertaining to Hurricane Katrina Flood Recovery is available through FEMA.
1 Campanella, R. (2007). Above Sea Level New Orleans: The Residential Capacity of Orleans Parish’s Higher Ground (D.J. Meffert ed.). A White Paper funded by the Coypu Foundation.