Tuesday, April 28, 2009

Levees cannot fully eliminate risk of flooding in New Orleans, study says

Science Daily: Levees and floodwalls surrounding New Orleans -- no matter how large or sturdy -- cannot provide absolute protection against overtopping or failure in extreme events, says a new report by the National Academy of Engineering and the National Research Council. The voluntary relocation of people and neighborhoods from areas that are vulnerable to flooding should be considered as a viable public policy option, the report says. If relocation is not feasible, an alternative would be to elevate the first floor of buildings to at least the 100-year flood level.

…Although some of the report's recommendations to enhance hurricane preparedness have been widely acknowledged for years, many have not been adequately implemented, said the committee that wrote the report. For instance, levees and floodwalls should be viewed as a way to reduce risks from hurricanes and storm surges, not as measures that completely eliminate risk. As with any structure built to protect against flooding, the New Orleans hurricane-protection system promoted a false sense of security that areas behind the structures were absolutely safe for habitation and development, the report says. Unfortunately, there are substantial risks that never were adequately communicated to the public and undue optimism that the 350-mile structure network could provide reliable flood protection, the committee noted.

Comprehensive flood planning and risk management should be based on a combination of structural and nonstructural measures, including the option of voluntary relocations, floodproofing and elevation of structures, and evacuation, the committee urged. Rebuilding the New Orleans area and its hurricane-protection system to its pre-Katrina state would leave the city and its inhabitants vulnerable to similar

….For structures in hazardous areas and residents who do not relocate, the committee recommended major floodproofing measures -- such as elevating the first floor of buildings to at least the 100-year flood level and strengthening electric power, water, gas, and telecommunication supplies.

…Furthermore, the 100-year flood level -- which is a crucial flood insurance standard -- is inadequate for flood protection structures in heavily populated areas such as New Orleans, where the failure of the system would be catastrophic. Use of this standard in the New Orleans area has escalated the costs of protection, encouraged settlement in areas behind levees, and resulted in losses of life and vast federal expenditures following numerous flood and hurricane disasters, the committee said….

Commander Mark Moran, of the NOAA Aviation Weather Center, and Lt. Phil Eastman and Lt. Dave Demers, of the NOAA Aircraft Operations Center, all commissioned officers of the NOAA Corps, flew more than 100 hours surveying Katrina’s devastation. All three men took dozens of aerial photos from an altitude of several feet to 500 feet.

1 comment:

Anonymous said...

The Science Panel's report also agreed with IPET findings that the outfall canal floodwalls fell down long before even being overtopped by storm surge waters because of elementary engineering design mistakes made by the US Army Corps of Engineers.

The most important recommendation was that the US Army Corps of Engineers reform to the extent that they would at least accept some small form of oversight from local government engineers, like the ability to review Corp designs of our flood control structures. Currently, the Corps cannot be trusted.

Regarding the report's elevation recommendations and smaller footprint idea. Isn't it irrelevant for them to say what we should have done? Families that were flood victims only had one shot at recovery. The Road Home Program is almost finished. Moronically, RHP is giving out elevation money last. Who could afford to wait this long? We already rebuilt. We did the best we could with what we had and built smaller, stronger and above the flood line.

Raised basement homes have always been very popular in New Orleans and now they are sprouting up like crazy in the Flood Zones. I bet you thought we were stupid, but it turns out that these big shot scientists took almost four years to recommend we do something we were already doing because we do have common sense. What these scientists didn't tell you is that the federal government determined Base Flood Elevation, that height government wants us to build, the height these scientists recommend, is about six feet lower than the flood line the Corps provided to us on August 29, 2005. Most families who have rebuilt elevated, have raised there homes above the Katrina flood line.