Turning a tragedy into large-scale barrier island restoration in Louisiana: A three-project case study

摘要

Louisiana has successfully utilized the proceeds from the fines imposed for the Deepwater Horizon incident to significantly jump start barrier island restoration as identified in the Coastal Protection and Restoration Authority (CPRA) of Louisiana Coastal Master Plan (CPRA 2017). The Riverine Sand Mining/ Scofield Island Restoration (BA-40) project was the first to be implemented through a commitment of remaining funds in the initial emergency protective berms' construction budget formulated into the Berms to Barrier Islands plan. The berm/ restoration conversion at Scofield Island was the first to utilize this funding mechanism. The Caminada Headland Beach and Dune Restoration-Increment II (BA-143) project was funded through the National Fish and Wildlife (NFWF) Gulf Environmental Benefit Fund and capitalized on a prior project constructed to the west completing the beach and dune restoration of the entire headland. Lastly, the Caillou Lake Headlands Restoration (TE-100) project was funded through the Natural Resource Damage Assessment (NRDA). The TE-100 project restored the entire degraded beach and dune system backed by a created marsh habitat to complement a prior restoration effort. Scofield Island is located west of the active Mississippi River bird's foot delta in Plaquemines Parish, Louisiana. A primary objective of this project was the excavation and delivery of Mississippi riverine sand for beach and dune restoration; a first in our nation's history. Multiple design and construction challenges arose requiring the CPRA, consulting team, and construction contractor to adapt. Construction of the beach and dune component of this project required approximately 22 miles (mi) of pipeline and four booster pumps along a sediment pipeline corridor that crossed two hurricane protection levees, went underneath two highways and a navigation channel, traversed the Empire Waterway, crossed Pelican Island, entered the Gulf of Mexico, and extended to Scofield Island. The restoration footprint length was approximately 2.4 mi, total volume placed was approximately 3.5 million cubic yards (MCY), and the benefit equaled 510 restored acres (CEC 2014). The pipeline corridor has subsequently been utilized for two other restoration projects, Shell Island East Berm Barrier Island Restoration (BA-110) and Shell Island West NRDA Restoration (BA-111). As a first in Louisiana's restoration history, the Caminada Headland Beach and Dune Restoration-Increments I and II (BA-45 and BA-143) utilized sand dredged from Ship Shoal, an Outer Continental Shelf (OCS) sand resource located approximately 26-38 mi from the restoration areas. The 13.3 mi long headland was restored with approximately 3.7 MCY for BA-45 and 5.5 MCY for BA-143 from the borrow area (CEC 2015 and CEC 2017). A combination of cutterhead dredge/scow barges and hopper dredges were used to construct the project. A key goal of this project was restoring and protecting the fragile ecosystem which provides critical habitat for nesting shorebirds. The headland is of critical importance in serving as a defense of our national energy infrastructure. The western portion of the headland directly protects Port Fourchon, one of the nation's most important energy ports. Caillou Lake Headlands (TE-100), known locally as Whiskey Island, is centrally located in the Isle Dernieres chain and it is a remnant of the single, larger Isle Dernieres (Last Island), which was segmented into multiple smaller islands by a major hurricane in 1856. The project included restoring the beach and dune along approximately 4.5 mi while simultaneously creating a marsh platform along approximately 5,500 feet (ft) utilizing 10.4 MCY of sand from the borrow area (CEC 2018). The borrow area lies within Ship Shoal OCS Lease Block 88 located over 10 mi along the conveyance corridor offshore of Whiskey Island. This project represents the largest barrier island restoration project to date in terms of volume per linear foot of shoreline with an average density of over 441 cubic yards per linear foot (CEC 2018).