The Giving Delta

Moffatt & Nichol | West 8 | LSU-CSS

 

Most coastal settlements occupy a tenuous line between water and land. They are strategically positioned on the ocean’s edge, but have to balance the consequences of coastal storms and increasingly the effects of climate change. However, the Deltaic Louisiana Coast has an opportunity that most other coastal regions do not: a dynamic, sediment-rich river that drains 40% of the contiguous US, that can continuously replenish this edge into a rich, productive wetland zone. While other cities are exposed to rising seas on fixed coastal edges, Louisiana can free itself from a century-long approach of flood control into one of controlled flooding and deposition, allowing the annual pulses of the Mississippi River to sustain a thriving wetland apron and allow for active land-building, protecting one of the Nation’s most crucial economic zones, enhancing ecosystem productivity, and nourishing human occupation for centuries to come.

On the ground today, the Delta is in dire straights and action is urgent. Due to the levees-only approach of the last century, land loss in Coastal Louisiana has reached a catastrophic point. Between regional subsidence, storm impacts, and Sea Level Rise, Louisiana is losing on average a football field of land every hour, or a total of 1900 Square Miles of Land since 1932, an area the size of Delaware. Without action, by 2100 Louisiana will have lost virtually all of its coastal wetlands. Moreover, the Nation’s shipping network, energy infrastructure, agricultural and energy exports and an irreplaceable cultural heritage which all depend on the River, are in very real danger of going underwater. 

In September 2013, Changing Course, with the support of the Army Corps of Engineers and the State of Louisiana launched a multidisciplinary design competition seeking innovative,yet implementable solutions to the threats facing the Louisiana Delta.  On August 20, 2015, the Moffatt & Nichol | West 8 | LSU-CSS Team was announced as a winning team in the Changing Course Competition. 

The Giving Delta project proposes six primary strategies that will bring a self-sustaining Delta into being over the next century. 

 

1. COUPLE ANNUAL RIVER OPERATIONS WITH LONG TERM ADAPTATION

The operation of The Giving Delta leverages the power of annual, naturally occurring floods, yielding maximum sediment capture from the River for wetland maintenance in the five estuarine Basins. On an annual basis, fisheries, communities and ecosystems can adapt to changing conditions, yielding a consolidated, sustainable Delta over the long term. 

 

2. SHIFT FROM FLOOD CONTROL TO CONTROLLED FLOOD

The Giving Delta proposes a paradigm shift from Flood Control to Controlled Floods. Structures built upriver of New Orleans pulse sediment and freshwater to neighbouring basins during high-water discharge, reducing salinity, improving ecosystem function, while continuing to reduce flood risk to New Orleans. Structures below New Orleans will operate passively, allowing sediment delivery to coastal basins when the river is high and restricting freshwater input when the river is low.

 

3. MOVE THE MOUTH OF THE RIVER INLAND

Shortening the River’s course to the Gulf keeps greater amounts of the River’s sediment in the littoral zone, reversing a century of sediment pouring off the continental shelf. Positioning the new channel 40 miles inland will protect the channel and catalyse investment in a new, state-of-the-art, globally competitive port complexsafely out of the area of highest subsidence. 

 

4. INEVITABLE TRANSGRESSION LEADS TO A CONSOLIDATED DELTA ZONE

Relative Sea Level Rise and reduced sediment retention are facts of today’s Delta. Taken together, these factors make the current Delta landscape too large to be sustainable. Practical, focused investment within a smaller, consolidated Delta Zone allows the wetland buffer zone to take advantage of sediment delivery during controlled flood-pulse event, concentrating land-building efforts. 

 

5. INVEST IN PORTS & SHIPPING IN A CONSOLIDATED WORKING DELTA

The Louisiana coastal zone is worth roughly $140 Billion annually to the United States—the same as the US Auto Industry. Economically speaking, this is not a local problem, but one of national import. The River at New Orleans is at the centre of an infrastructural network that connects the country and feeds the world. A plan for the next century of port investment and improvement starts with the relocation of Port facilities inland to Port Sulphur. A two-pronged shipping channel design improves shipping efficiency and allows for the Mississippi River corridor to compete globally with deeper channels and modernized facilities.

 

6. LINK COMMUNITY INFRASTRUCTURE IN A RESILIENT AND ADAPTIVE NETWORK

The Giving Delta proposes linking every dollar spent to multiple improvements along key spines such as the I-10, US-90, I-45, and the GIWW. Community Development Investments will be linked to infrastructure, transportation, and environmental management, ensuring that a viable Working Coast is also guaranteeing long-term liveability and resilience of major settlements. 

A host of engineering and design tactics were studied, bringing these strategies to level of realism that demonstrates this project is implementable. Sand Motors and barrier islands harness longshore and offshore coastal processes to keep sediment and sand in the littoral zone for the long term. Investment in the Gulf Intercoastal Waterway underpins the importance of a key commercial and industrial corridor while allowing for inter-basin management of salinity levels. Structures such as passive spillways and controlled floodways are carefully sized for projected flood levels that maximize sediment deposition while keeping salinity levels within the tolerance of oyster beds, commercial fisheries, and native ecosystems. Sediment traps and dedicated dredging allow active control and placement of precious sediments to the areas within the Coastal Zone where it is needed most urgently for economic and residential protection. 

For more information: www.changingcourse.us


CLIENT

Environmental Defence Fund with the support and participation of the State of Louisiana and U.S. Army Corps of Engineers

 

PARTNERS

Moffatt & Nichol, LSU Coastal Sustainability Studio, Deltares, Ioannis Georgiou, Headland & Associates, RAND

 

ALL IMAGES CREDIT

Moffatt & Nichol | West 8 | LSU-CSS