Protecting New Orleans: Revision of the hurricane protection system in order to prevent lake borgne induced flooding during hurricanes

On the morning of August 29, 2005, Hurricane Katrina struck New Orleans. A storm of Katrinas strength and intensity is expected to cause major flooding but the main portion of the destruction was caused by its exposure to failures at almost all levels of responsibility. In Katrinas wake, a Grand Plan for Louisiana is introduced by the Louisiana State University. In this thesis, the confluence of the Mississippi River Gulf Outlet (MRGO) and Gulf Intracoastal Waterway (GIWW) is analyzed. It is recommended to implement two flood protection structures in combination with a straight levee alignment between them. This option has the best high water safety and most positive ecological influence. It is concluded that closing the MRGO is the favorable option for the future development. The GIWW is highly navigated and should remain open A vertical lifting gate is chosen as optimal flood protection structure. Its hoisting system is complex but well known, providing a reliable closure system. It can also safely discharge excess water, which represents a main functional requirement. Quantifying time dependent processes leads to conclude that the optimal combination is a gate height of +30 ft (10.6 m, MSL) and leakage width of 0.05 m at the sides and 0.15 m at the bottom. This has the benefit that no perfect closure is needed during a storm event, which reduces the need for maintenance and increases the reliability of the closing process. In the design of the steel lifting gate reference is made to the Hartel Canal Barrier, a proven protection scheme in the Netherlands. The total mass of the gate amounts 1060 tonnes. The main contributors are the bottom and center lens-shaped barrier sections. The front plate forms the largest single contributor at 20% of the total mass of the gate. The upper lens-shaped barrier section requires only 40% of the steel volume needed for the leading lens-shaped sections and results in a weight reduction of 126 tonnes. Major problems due to the lifting gate vibration in vertical direction are not expected as the system is positively damped and the excitation frequency is sufficiently small compared to the first Eigen frequency.Civil Engineering and Geoscience