The U.S. Army Engineer District, New Orleans is determining the correct sizing for sail-through structures to be constructed along the new proposed Morganza to the Gulf levee system in southern Louisiana. In the aftermath of Hurricane Katrina, numerous new levees are being constructed to reduce the risk of storm-induced flooding. In addition to the economic and loss of life impact of such flooding, there is also a significant negative impact on the local ecosystem. To provide the best protection, waterways north of the new levee system will be shut off from the Gulf of Mexico during storm events. In order to accomplish this protection with minimum impact on the natural environment and waterborne transportation, numerous sail-through structures - each capable of being closed as necessary - are being constructed to allow for continued waterborne transportation between the Gulf of Mexico and areas north of the new levee system. These structures will also allow for the continued movement of water to and from the Gulf of Mexico, thereby minimizing the impact of the new levee system on natural habitat. Also included along the levee system are numerous environmental structures to increase the connection between the Gulf of Mexico and areas north of the proposed levee system during normal tidal exchange. At the request of the New Orleans District, the U.S. Army Engineer Research and Development Center (ERDC) performed a number of engineering studies in support of efforts to determine the proper sizes of six proposed structures (Bush Canal, Bayou Terrebonne, Lapeyrouse Canal, Placid Canal, Bayou Petit Caillou, and Humble Canal). These structure sizes will be determined through numerical modeling using the Adaptive Hydraulics Code (AdH). More information can be found in ERDC/CHL TR-11-6.