HR: 09:30h
AN: U31B-06    [Abstracts]
TI: Flood Risk in Megadelta Coastal Cities: Lessons From New Orleans
AU: * Ward, R E
EM: bob.ward@rms.com
AF: Risk Management Solutions, Peninsular House 30 Monument Street, London, EC3R 8NB, United Kingdom
AU: Muir-Wood, R
EM: robert.muir-wood@rms
AF: Risk Management Solutions, Peninsular House 30 Monument Street, London, EC3R 8NB, United Kingdom
AU: Grossi, P
EM: patricia.grossi@rms.com
AF: Risk Management Solutions, 7015 Gateway boulevard, Newark, CA 94560, United States
AB: The flood hazard posed by storm surges to the city of New Orleans is increasing for three reasons. First, as a result of the city's location on thick deposits of recent delta sediments along the edge of an oceanic basin, it is sinking at geologically rapid rates. Second, over the last decade, global sea level has increased as a result of climate change and is projected to continue to rise in the future. And third, the level of Atlantic basin hurricane activity has also increased, with the biggest increase for the strongest storms (with the largest surges), particularly in and around the Gulf of Mexico. The future flood risk in New Orleans has been explored using stochastic hurricane and storm surge generation models. Levels of risk have been determined at different geographical locations within the city today, and have been estimated for the future based on likely changes in the flood hazard. The study has also incorporated vulnerability and breaching models to determine the probabilities of failure and likely breach size, relative to the height of the storm surge outside, for each section of the flood defences that protect the city. Flood maps of relative risk throughout the region were developed from high resolution digital elevation maps, showing expected flood depths at various return periods. For example, the map for the 100-year return flood shows the extent of flooding that is expected on average once every 100 years, corresponding to an annual exceedance probability of one per cent. Additionally, four locations within the city of New Orleans were chosen for a more detailed study of predicted flood depth return periods, using the simple metric of the modeled return period of first flooding from a storm surge. The study shows that while the risk of flooding from storm surges can be reduced by the repair and enhancement of flood defences, the risk will begin to rise again as soon as improvements stop. The situation in New Orleans raises wider questions about the viability of megadelta coastal cities that are faced with the impacts of climate change.
UR: http:www.rms.com
DE: 1817 Extreme events
DE: 1821 Floods
SC: Union [U]
MN: 2007 Joint Assembly