Title: Feasibility and Design for the Increase Atchafalaya Flow to Terrebonne Diversion
Project
Preferred Presentation Type: Oral Presentation
Freshwater and sediment in the Atchafalaya River, in southern Louisiana, are currently confined to the leveed river until released well south of Morgan City into the Atchafalaya Bay.
Confinement of the river, in combination with high rates of subsidence and rising seas, has resulted in salt water intrusion and marsh degradation. The Increase Atchafalaya Flow to
Terrebonne Project was proposed to utilize freshwater and sediment from the Atchafalaya River to build, sustain and maintain wetlands in the sediment-starved deltaic basin to the east of the river’s levee. A key component of the project is a 550 m 3
/s freshwater diversion intended to hydrologically influence 200,000 hectares of wetlands, and slow the current wetland loss being experienced in the basin.
Moffatt & Nichol developed a Wetland Morphology Module (WMM) for the comparison of project alternatives. This WMM is used to model the long-term effects of each alternative on salinity propagation throughout the Terrebonne wetlands, as indicated by changes in vegetation, land cover and open water. The WMM is coupled with a 2D hydrodynamic model and is used to evaluate the evolution of marsh types over time under the stressors of hydro-period and salinity on a high-resolution scale. In short; the WMM determines whether wetlands will survive, collapse or switch from one wetland type to another. The WMM dynamically couples and provides direct feedback to the spatial distribution of vegetation and land cover changes in long term (50 year) hydrodynamic analyses.
Modeling to date predicts the project will remediate and offset increased saltwater intrusion and high subsidence rates which have significantly contributed to wetland loss in this Louisiana basin. By the end of 2015 it is anticipated that the feasibility phase for the project will be completed and the engineering and design phase have begun.
Session Topic:
RESTORE, NFWF, and NRDA Projects
OR
Lagoon, Wetland, Marsh, and Estuary Restoration and Enhancement
Keywords: Louisiana, Atchafalaya River, wetland morphology, wetland restoration, river diversions, sea level rise, planning, feasibility
Authors Information:
Maarten Kluijver, Moffatt & Nichol, 301 Main Street – Suite 800, Baton Rouge, LA70825,
Louisiana, USA; mkluijver@moffattnichol.com
, 225-336-2075
Austin Feldbaum, Louisiana Coastal Protection and Restoration Authority, Baton Rouge,
Louisiana, USA, austin.feldbaum@la.gov
; 225-342-4594

Presenter biography:
As a Coastal Engineer Mr. Kluijver specializes in coastal protection and restoration and associated hydraulic and morphological modeling. He has a thorough knowledge of coastal and riverine processes, regional sediment management, and coastal flood protection.
Today, his coastal engineering project portfolio includes studies on coastal hydrodynamics and morphodynamics. These studies are developed to enhance flood protection systems, and to design a more effective response to coastal erosion, restoration and preservation on behalf of
Moffatt & Nichol’s clients, most notably the Coastal Protection and Restoration Authority of the
State of Louisiana. Mr. Kluijver is project manager for the "Increase Atchafalaya Flow to
Terrebonne" project.