Wildlife Insider Spring Summer 2010 - Louisiana Department of ...

Figure 2. Land change 1887 vs. 1996 (Penland et. al. 2003)as protection for coastal communities by reducingstorm surge associated with tropicalstorms and hurricanes.According to the National WetlandsCenter, the Terrebonne Basin, which includesIDBIR, has the second highest erosionrate in Louisiana (Barras et al. 1994)(Figure 2.). It has experienced as much as10.2 square miles of loss per year over thelast few decades. Barrier islands are part ofthe final stages of delta degradation and arequite vulnerable to erosion. According toMcBride et al. 1989, the Isle Dernieres barrierisland chain is the most rapidly erodingcoastline in the United States. A study byPenland et al. 2003 indicated that IDBIR isexperiencing an average shoreline erosionrate of 38.7 feet per year on the gulf sideand 8.2 feet per year on the bay side of theislands. Due to the extensive wetland loss atand in the vicinity of IDBIR, over 85 milliondollars have been spent or allocated tokeeping IDBIR from becoming a subaqueousshoal.Coastal restoration at IDBIR began in1991 when Wine Island was recreated bypumping dredge material from the HoumaNavigation Canal onto the remnants of theisland which had eroded to a shallow shoal.The project was funded via the Water ResourcesDevelopment Act of 1986. The areawas wrapped with a rock dike and materialwas pumped to a +4 feet to +7 feet elevation.Also in the early 1990s, the developmentof large scale beach/marsh restorationprojects were initiated via the Coastal WetlandsPlanning Protection and RestorationAct (CWPPRA). In 1999, the Isle DernieresRestoration East and Trinity IslandsProjects (TE-20 and TE-24) were created.These projects were designed to rebuildportions of these islands using a hydraulicdredge. The projects included marsh creation,dune creation, sand fences to trapwind blown sand and vegetation plantings.Subsequently, the Whiskey Island RestorationProject (TE-27) was constructedbetween 1998 and 2000. This project alsoutilized a hydraulic dredge to create a dune/marsh platform and fill in a breach of theisland (approx. 657 acres). The project alsoincluded installation of sand fences andvegetation plantings. In 2007, a secondhydraulic dredge project was implementedat Trinity and East Islands (New Cut Duneand Marsh Restoration Project, TE-37).This project included marsh and dune creation,beach nourishment, installation ofsand fences and planting of native vegetation.The primary objective of this projectwas to solidify a breach between the twoislands by widening the island in an areaknow as “New Cut.” Also in 2007, materialwas pumped from the Houma NavigationCanal to Wine Island in an effort to beneficiallyuse dredge material to widen theisland. Unfortunately, this project had minimalbenefits due to the low quality of materialpumped from the navigation channeland impacts from hurricanes Gustav andIke. Overall, these projects were critical forthe longevity of the islands. Without restoration,the islands were expected to disappearby 2004 (McBride et al. 1989).A majority of restoration at IDBIR utilizeda hydraulic dredge to borrow sedimentfrom water bottoms to nourish thebeach and bayside marshes of the islands.However, a different technique was utilizedfor Raccoon Island. In 1997, eight segmentedbreakwaters were constructed usinglarge boulders along the gulfside of theisland to reduce erosion (Raccoon IslandBreakwaters Demonstration Project, TE-29) (Figure 3). This technique proved tobe a successful way of decreasing erosionrates and, as a secondary/unanticipated effect,resulted in the trapping of sand depositswhich increased the width of the island.Subsequently, eight additional breakwatersand a rock groin were added in 2007 toprovide additional shoreline protection andtrap sediment (Raccoon Island ShorelineProtection/Marsh Creation Project, TE-48).This project also includes a second phasethat includes a marsh creation component(60 acres) and vegetation plantings. Thisphase of the project was expected to be initiatedin late 2009 or early 2010.In 2009, the preservation of IDBIR continuedwhen a second restoration project atWhiskey Island was initiated. On February11, the Louisiana Office of Coastal Restora-Photo courtesy of Weeks MarineDredge and material pumped into dune creation site.Winter 2010LDWF file photo5