Bayou Shoreline Protection and Marsh Creation

The Freshwater Bayou Canal provides major shipping access from the Gulf of Mexico to Louisiana’s Intracoastal Waterway. Wakes from vessels traveling the canal have eroded the shoreline, exposing interior marshes to increased saltwater intrusion, wake impact and tidal scour, which, in turn, have depleted organic marsh soils and destroyed vegetation.

GeoEngineers provided a comprehensive geotechnical investigation and engineering recommendations to help protect the Bayou Canal shoreline and create approximately 100 acres of marsh adjacent to the Freshwater Bayou.

Approach

• Explored soil conditions in the canal and marsh area using a pontoon-mounted drilling rig and marsh buggy
• Designed a solution involving rock dikes at designated areas along the canal to protect the shoreline from wake and tidal action
• Developed design solutions to maximize the height and weight of rock dikes in areas of soft clay soil
• Designed earth dikes to create marsh ponds adjacent to the Freshwater Bayou Canal and recommended pumping fill from the canal into the interior marsh ponds to help create needed habitats
• GeoEngineers returned to the site in 2014 to instrument and monitor the marsh-creation area prior to and during placement of the marsh fill. GeoEngineers has partnered with a surveying team to track settlement of the marsh creation area at the fill surface, at the mudline and at several points below the mudline over the next few years.

Results

• The rock dikes range in height from three feet in the softest soil areas to seven feet for the strongest soil. The protective dikes are designed to dissipate wave energy, thereby reducing shoreline erosion.
• Recreated approximately 100 acres of marsh near Freshwater Bayou, enabling the surrounding basin to function as a freshwater marsh habitat.
• GeoEngineers completed its portion of the project for the Louisiana Department of Natural Resources on time and on budget.