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What works: Marshland restoration

A recent Tulane University study painted a bleak picture for the future of Mississippi River delta marshlands as global sea levels rise. The study said that damage may be irreversible and that marshlands along the Louisiana coast could drown in as little as 50 years.

It’s a distressing report that raises red flags for the long-term health of part of the coastal ecosystem that is vital to tempering sea-driven storm energy and to providing a home for a variety of aquatic life forms.

In an effort to offer an antidote to Tulane’s bleak assessment, let’s take a look at two projects that, although small in scale, suggest that options do exist to restore and rebuild these vital natural systems.

Almost 20 years ago, the U.S. Army Corps of Engineers created Evia Island in Galveston Bay. Since the 1980s, the Bay has lost more than half of its salt marsh habitat and most of its natural nesting islands due to subsidence, erosion and development.

The project involved using material dredged by the Corps from the Bay as part of ongoing work to keep shipping channels at their specified depths.

The Corps dumped dredged sediment within a barrier to create 2,800 acres of marsh and a six-acre mixture of scrub shrub and wetland habitats. After the island was established, sustainable landscaping and cover were added to help attract birds to the island.

Brown pelicans on Evia Island in Galveston Bay. A rock barrier forms a lagoon. Credit: Houston Audubon

For example, part of the bird habitat was planted with trees and shrubs. A lagoon was included that is regularly flushed by tidal action. Rock armor around the island offers a useful habitat for crustaceans. The island is now managed and maintained by Houston Audubon and provides an environment for rare and endangered coastal birds.

A second example comes from the Netherlands, which has centuries of experience dealing with the sea.

At the country’s far northeast coast, salt marsh development has been underway since 2014 using sediment from the Port of Delfzijl and the Dollard Estuary. The project aims to improve a variety of natural habitats, contribute to the region’s economy and enhance flood protection efforts by mitigating the effects of subsidence and sea level rise.

The project was commissioned by the municipality of Delfzijl and it is part of the “Marconi Buitendijks” regional development. (Watch a video that outlines the project’s main features.)

The experiment used different percentages of fine sediments and tested various types of wave-attenuation structures, such as semi-permeable barriers. The marsh is expected to reduce the energy of storm waves and help reduce the load on a levee that stands between it and the city.

Only a pioneer-stage salt marsh is being created. Natural processes are expected to play a dominant role in providing sediment. Over time, the pioneer salt marsh is expected to naturally grow into a mature salt marsh.

Aerial view of the Marconi salt marsh restoration project in progress. Credit: Wadden Sea Ports

To be sure, these projects are modest in scale (especially so when compared against the scale of marshland loss detailed in the recent Tulane report).

But they offer useful models that must be considered for widespread adoption by NGOs, municipalities and corporate partners like the Gulf Coast’s oil and natural gas interests.

Projects like these may carry a high price tag if they are seen only in the context of a budget line item. The protection they offer to commercial fishing as well as to inland cities and towns tips the scales by many times over the expense of recovering from a major flooding event.

Sea levels are rising. So, too, should the sense of urgency to deploy nature-based solutions like these.

What do you think? Join the conversation! theinfrareport@gmail.com

The graphic is an overview of the Netherlands salt marsh development project. Thanks to EcoShape for the image!

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Author: David Wagman

I live in Colorado where I write about a wide range of topics, and get outside regularly to hike, bike, garden and walk the dog!

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