Seabrook and Borgne Alignment Construction Sequence Hydrodynamic Study

摘要

The U.S. Army Corps of Engineers (USACE) Hurricane Protection Office (HPO) is authorized to provide New Orleans, Louisiana, with a risk reduction system for the one percent exceedance flood (HSDRRS). The purpose and need for the proposed action is to provide, in a timely manner, the 100-year level of risk reduction from flood damage to the areas surrounding the IHNC due to flooding from hurricanes and other severe storm events. This risk reduction is being accomplished through the construction of a comprehensive system of levees, gates, and drainage structures. Several planned structures (to be located along the levee system) allow for continued navigation in the Inner Harbor Navigation Canal (IHNC), Bayou Bienvenue, and the Gulf Intracoastal Waterway (GIWW). The IHNC Seabrook, Bayou Bienvenue, and GIWW gate structures are designed to remain open during normal tidal conditions with the ability to close during surge events. Numerical model studies were performed by the USACE Engineer Research and Development Center (ERDC) Coastal and Hydraulics Laboratory (CHL) to assess the impacts of these navigation structures on hydrodynamics and larval transport. HPO requested that ERDC also perform a numerical modeling study for the purpose of analyzing the temporary construction impacts of proposed HSDRRS measures to be placed in the GIWW and the Mississippi River Gulf Outlet (MRGO). The work presented in this report documents hydrodynamic modeling and analysis of two construction sequence plans which will occur during the construction of the Borgne alignment and Seabrook structures included in the HSDRRS. This report specifically focuses on the construction sequence plans during which the Bayou Bienvenue structure and GIWW sector gate are being built as well as the construction of the Seabrook structure. The February 2010 plan includes cofferdams on the Bayou Bienvenue.