GeoCarta Has Moved

Dec 5, 2005

Government Agencies Muddy The Water With Conflicting Directions On New Orleans Flood Heights

Federal agencies continue to offer conflicting advice on what elevation datum and flood elevation height should be used in the New Orleans area, causing confusion as to what elevation standard buildings should be constructed to, the New Orleans Times-Picayune reported today. In the mean time, local officials continue to approve permits for rebuilding, knowing that they are basing such decisions on inaccurate, out-dated maps. While residents struggle to begin rebuilding, various federal and local agencies offer conflicting advice on just how high new building should be, or even what datum should be used.

National Oceanic and Atmospheric Administration (NOAA)
I posted previously that NOAA had published new, lower elevations for benchmarks for the parishes in the New Orleans area. These new elevations are part of a new network of vertical controls in the area. The agency emphasized that these new elevations should be used in rebuilding along the Gulf Coast. Not only do NOAA's elevations take into consideration the latest information on gulf coast subsidence, it is referenced to the North American Vertical Datum (NAVD) of 1988, a better model of the earth's surface.

Federal Emergency Management Agency (FEMA)

FEMA's Flood Insurance Rate Maps are still referenced to the National Geodetic Vertical Datum (NGVD) of 1929. Not only is the 1929 model inferior to more modern ones, FEMA's maps fail to reflect the effect of subsidence on the area, which some experts estimate could be as much as one-half inch per year. It is believed that actual flood elevations may be from one to two feet higher than are currently shown on the New Orleans area flood maps. Though they may be outdated and inaccurate, the current flood map remain the legal standard by which rebuilding efforts are held to.

According to the Times-Picayune, FEMA hopes to issue informal advisories in the coming weeks, based on new elevation studies. The paper quotes FEMA official Ross Richardson, as saying, "The (hurricane) events show some inaccuracies in our existing maps. We're trying to give the best information possible to the communities so they can consider it for reconstruction purposes." However, officially adopted and updated Flood Insurance Rate Maps are not expected from FEMA until sometime in 2007. FEMA says that they are waiting until they see what the Army Corps of Engineers is going to about the New Orleans levees.

Local Officials
It appears to be business as usual among local governments charged with permitting rebuilding projects and protecting their citizens from floods. The Times-Picayune reports that officials in some parishes are accepting older Elevation Certificates and allowing damaged homes to be rebuilt at their pre-Katrina elevations. In the City of New Orleans, Greg Meffert, executive assistant to New Orleans Mayor Ray Nagin, told the Times-Picayune that old flood elevation certificates can be used to secure building permits, and that in some cases where a resident's flood certificate is missing, building officials have been told to let the project proceed if there is other evidence that a home is roughly in line with flood-elevation requirements.

Another Flood?
While bureaucrats study the situation, politicians continue to insist that the rebuilding effort move forward, with or without sound data. The situation leaves open the possibility that many residents will rebuild their homes and businesses below the actual 100 year flood elevation, exposing their property to more flood damage in the future.