CPRA Presents Louisiana Coastal Basins Report
Louisiana’s coastal basins need help, the state Coastal Protection and Restoration Authority (CPRA) reported at the biennial State of the Coast Conference at the New Orleans Morial Convention Center yesterday.
During a panel discussion led by CPRA Operations Chief Ignacio Harrouch, officials also said that much has been done in each of the basins, and CPRA has plans to do even more through projects outlined in its 2017 Coastal Master Plan.
The 2.75 million acre Pontchartrain Basin encompasses the area of the Maurepas Swamp, Lake Pontchartrain, Laplace, New Orleans, Slidell, Lake Borgne and out to the Chandeleur Islands. Since 1932 the basin has lost approximately 131,000 acres of wetlands (17 percent), with more than 608,000 acres of wetlands remaining.
“The degradation of the marshes and swamps is due to a number of factors common along our coast,” said CPRA’s New Orleans Regional Operations Manager John Troutman, “including a lack of fresh water and sediment from the Mississippi River, shoreline erosion, subsidence, sea level rise, and the loss of land formations and the subsequent hydrological impacts.”
Troutman outlined some CPRA projects intended to combat these effects, including the recently completed Bayou Bonfouca Marsh Creation; projects to restore and save the Orleans Landbridge separating Lake Pontchartrain from Lake Borgne; the Golden Triangle Marsh Creation project to restore 600 acres of marsh near the intersection of the Intracoastal Waterway and the MRGO; the Lake Borgne Marsh Creation Increment One project to restore more than 1,500 acres of marsh near Shell Beach; and the planned River Reintroduction Into Maurepas Swamp to add needed fresh water and nutrients to save an existing environment while it is still in good shape.
BRETON SOUND BASIN
The Breton Basin has experienced a 38 percent loss of land with more than 105,000 acres disappearing since 1932, the second-highest percentage of land loss in any of our coastal basins, Troutman reported.
CPRA is pursuing a permit to build a controlled, gated structure in the Mississippi River levee above Wills Point in Plaquemines Parish to divert river sediment into the basin. Troutman said that CPRA must comply with more than 70 environmental rules and permits. The Corps is in charge of conducting an Environmental Impact Statement. If permitted to go forward, construction would not be completed until 2025 at the earliest.
MISSISSIPPI RIVER BASIN
This region encompasses the vulnerable bird-foot delta of the lower Mississippi River. It has experienced the greatest percentage land loss of any coastal basin, declining from 171,000 acres to just 78,600 acres—a 55 percent decrease in land mass since 1932.
“An excellent example is our partnership agreement with the Corps of Engineers on the Tiger Pass project. The beneficial use of dredged sediment is restoring approximately 5,000 linear feet of historic ridge running along the north side of Spanish Pass, backed with a 500-foot-wide marsh platform. CPRA is putting up $4.5 million of the projected $18.1 million cost of the project.”
Troutman also cited lessons learned about diversions and land building in West Bay where a CWPPRA project intentionally crevassed the levee above Head of Passes. Land was built more expeditiously once the Corps dredged berm-type islands to slow the rate of flow within the bay, allowing sediment to drop out and noticeably accrete.
BARATARIA AND TERREBONNE BASINS
Between the Atchafalaya and Mississippi Rivers lies an area of approximately 5,700 square miles, comprised of two basins bisected by Bayou Lafourche: Terrebonne Basin to the west and Barataria Basin to the east.
These basins have seen the most extensive projects in state restoration history, including dredging and placing more than 67 million cubic yards of sediment from the Mississippi River and offshore sources, and the expenditure of more than $761 million to rebuild our first line of defense, the barrier islands and headlands at the perimeter of the basins, including the reconstruction of East Grand Terre, Bay Joe Wise, Scofield Island, Pelican Island, Shell Island, the Caminada Headland and Elmer’s Island, West Belle Pass, East Island, Trinity Island, Raccoon Island, and Timbalier Island and East Timbalier Island.
An additional $244 million in projects are now in engineering and design to add to the restoration of the basins’ perimeter, Dearmond reported.
ATCHAFALAYA AND TECHE/VERMILION BASINS
These basins are unique among the Louisiana coastal area in being relatively geologically stable, benefiting from the Atchafalaya River, reported Glenn Ledet, Jr., the Assistant Administrator of the CPRA Operations Division.
Ledet highlighted some of CPRA’s projects now in the construction phase, including the Coles Bayou Restoration project to create more than 400 acres of marsh and to install a series of culverts at nine locations to increase the inflow of fresh water and sediment; and improving pump stations and levees protecting Morgan City from Lake End to Justa Street as well as raising the elevation of 2,100 feet of Louisiana Highway 70.
A study was completed to assist project planning for levee districts in the basins. It evaluated levee alignments across Iberia and St. Mary Parishes to reduce potential flooding and examining the possibility of upgrading the river levee system in St. Mary Parish that has proven deficient in protecting the area from tropical and hurricane storm surges.
A longer-range planning effort is also evaluating the benefits of increasing the eastward flow of fresh water from the Atchafalaya River system in the vicinity of the Bayou Boeuf Lock.
CALCASIU/SABINE AND MERMENTAU BASINS
All or parts of the parishes of Vermilion, Cameron and Calcasieu make up the vast basins covering the southwest corner of Louisiana. More than 768,000 acres of wetland habitat stretch from the Sabine River bordering Texas to the Intracoastal City area along Freshwater Bayou.
“It is a very watery environment,” said CPRA Lafayette Regional Operations Manager Darrell Pontiff, “and therein could lie the problem if things continue unabated: too much water and not enough land.”
Pontiff spoke of several projects to mitigate the damage. Shoreline protection projects on the coast in Cameron Parish have delivered nearly two million cubic yards of offshore sand to rebuild the beach perimeter in front of vital Highway 27, and more offshore sand was used over 800 acres of the most vulnerable marsh behind that highway at Oyster Bayou.
Hundreds of millions of post-BP oil spill money is to be used for salinity control in the Lake Calcasieu Ship Channel, while additional projects for marsh creation freshwater introduction are underway or in engineering and design. Pontiff also highlighted a project just entering the construction phase on the shoreline in front of the Rockefeller Wildlife Refuge.