Risk to life due to flooding in post-Katrina New Orleans

After the catastrophic flooding of New Orleans due to hurricane Katrina in the year 2005, the city’s hurricane protection system has been improved to provide protection against storms with at least a 100 year return period. This thesis investigates the risk to life in the post-Katrina situation for the New Orleans metro bowl. The risk to life is evaluated through a ‘scenario’ based approach simulating defined flood events. Several scenarios are identified that could lead to flooding within the Metro Bowl and including the failure of hurricane protection or the river levees. The probability for each scenario is determined based on existing design guidelines and expert judgment. A two-dimensional hydrodynamic model is used to simulate flood characteristics and these outcomes are used as input for the loss of life estimate. In addition, the evacuation effectiveness has been considered. Results indicate that the estimated loss of life in case of flooding ranges from about 100 to nearly 500. The highest life loss value is found for breaching of the river levees. The probability and consequence estimates are combined to evaluate the individual risk and societal risk for New Orleans. The individual risk (IR) refers the probability of an individual residing in a given area perishing as a consequence of flooding. The IR for large parts of New Orleans metro is larger than 1/100,000 per year. The evaluated risk is compared to risk levels that have been found to the risks of other large scale engineering systems (e.g. other flood prone areas in the US and other regions, dams and the nuclear sector) as well as existing criteria for evaluating acceptable levels of individual and societal risk. The evaluated risk determined in this study exceeds tolerable or acceptable risk criterion as discussed in literature and other industries. Despite the major improvements to the flood protection system, the societal flood risk of New Orleans is still expected to be significant at a national (US) scale. Finally, the effect of various risk reduction measures on the risk level is investigated. Strategies for which costs and risk reduction effects are discussed, including: elevated homes, improved evacuation and increased protection ( relocation of population to higher areas). While decisions regarding flood risk are complex and involve many factors such as perception and economic considerations, the results indicate the necessity of further discussion regarding the management and reduction of the city’s risk to flooding.Hydraulic StructuresHydraulic EngineeringCivil Engineering and Geoscience