Katrina Cut

Coastal Engineering

The Katrina Cut temporary berm project was a test of Thompson’s coastal engineering agility and expertise. Named after the hurricane that created it, Katrina Cut was a 1.5 mile wide gap on the west end of Dauphin Island. The gap, which split the main body of the barrier island, was left untouched until another disaster forced action. The BP Deepwater Horizon oil spill in the Gulf of Mexico initiated the emergency response project. Worried that oil from the spill would pass through Katrina Cut and contaminate oyster beds and estuaries in Mississippi Sound and Portersville Bay, the State of Alabama authorized the design and construction of a berm to fill the gap. After facilitating emergency permitting and approval in just 8 days, Thompson Engineering designed and began construction of an 8,400 foot-long, sand-filled, rock-rubble berm. The project involved the placement of approximately 150,000 tons of Grade “A” stone, 95,000 cubic yards of hydraulically excavated and placed sand, and 110,000 tons of armor stone. The top of the sand core sits at +5 feet above sea level with a three feet thick armor layer on top of the sand. The top of the berm is approximately 20’ wide at elevation +8.  The berm’s bottom width varies according to water depth and is 84 feet at its widest.

While Thompson Engineering worked to beat the oil headed in Dauphin Island’s direction, it engaged in other environmental consulting issues as part of the Katrina Cut project. The design incorporated protection of multiple oil and gas pipelines that run through the project area, and included methods to attach the berm to the existing terrain to prevent erosion and bypass during future storm events. In addition, teams located and protected nesting shorebirds, sea turtles and submerged aquatic vegetation beds.