Pass-A-Loutre, Louisiana Sediment Diversion Project

HNTB has worked to save or restore Louisiana’s coast for the past 30 years, where the wetlands have been eroding at a rate of one football field every 45 minutes.

In an area known as the Pass-a-Loutre, state officials sought to harness the natural cycle of the Mississippi River Delta in order to rebuild land mass in a wildlife area. The project would divert sediment-rich river water through man-made cuts along the water’s edge. It was hoped that over time layer upon layer of sediment would accumulate and eventually form new land.

The project entailed three strategic cuts, or crevasses, in the natural levees along the Mississippi River to divert sediment into the wildlife area. HNTB conducted surveys, selected crevasse sites, developed designs and monitored construction. During the planning stages, HNTB conducted an extensive evaluation of potential crevasse sites to capture the most sediment for wetland building.

More than 30 years after the original cuts were made, the initiative has proven to be a resounding success. To date, the Pass-a-Loutre Marsh Creation Project has created and sustained 760 acres of land and thousands of acres of submerged aquatic vegetation — resulting in one of the most cost-effective coastland restoration projects in U.S. history.

• HNTB led engineering and design
• Project diverts sediment-rich river water through manmade cuts
• Wetlands protect levees, which in turn protect cities