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 RSS has issued the following assessment of New Orleans flood risk.
On August 25, 2005, Hurricane Katrina first made landfall on the Florida Peninsula as a moderate Category 1 hurricane. Devastating the city of New Orleans, Katrina made landfall again as a strong Category 3 storm on the morning of August 29, 2005. Although the storm weakened as it passed through the city, it maintained the characteristics of a Category 5 hurricane offshore, causing storm surge to reach maximum elevations of more than 25 ft (7.6 m) along the south-facing Mississippi Coast. Because Katrina exceeded the standard surge for a Category 3 hurricane (the ‘standard project’ Category 3 hurricane was used to design the city’s flood defenses), some of New Orleans’ levees and pumping systems failed.
“Hurricane Katrina was one of the most destructive natural disasters to occur in the United States, but also one in which large amounts of the damage and loss of life reflect the failings of human systems of engineering, planning, and disaster management,” said Dr. Claire Souch, vice president of Natural Catastrophe & Portfolio Solutions, RMS.
A number of investigations have already been conducted in order to understand these failings, with the results published in FEMA, 2006; ILIT, 2006; USACE, 2006. Each stressed the need to identify lessons to be learned from the disaster to reduce the chances of a recurrence in the future. A number of major points have emerged relating to flood risk in New Orleans, stressing the need for risk-based approaches to flood management.
Since Katrina, a significant amount of reconstruction and strengthening of the levee systems in New Orleans has taken place, with several billions invested. The US Army Corps of Engineers is committed to providing a 100-year level risk reduction for southeast Louisiana in 2011 through its Hurricane and Storm Damage Risk Reduction System (HSDRRS). A 25 ft-high surge barrier is being constructed eight miles east of the city, where the Gulf Intracoastal Waterway (GIWW) and the Mississippi River Gulf Outlet (MRGO) meet.
However, while steps have been taken to prevent a similar reoccurrence, the flood threat to New Orleans continues to increase due to a combination of three factors:
New Orleans is located on thick, relatively young delta sediments along the edge of an oceanic basin; the city is sinking at geologically rapid rates. Over the last decade, global sea level rise has increased as a result of climate change and is predicted to accelerate in the future. The level of Atlantic Basin hurricane activity has also risen, with the biggest increases for the strongest storms (with the largest surges).
These factors all serve to increase the storm surge flood hazard faced by New Orleans, and will significantly raise the risk of flooding in the city through the 21st century.
•Date: 31st August 2010 • Region: US •Type: Article •Topic: DR general
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