ECU researchers study marsh loss impact on waterfowl

A team of East Carolina University researchers is investigating how marsh loss, shoreline erosion, altered water movement and sea level rise are creating concerns for wildlife habitat and flooding on Mackay Island National Wildlife Refuge in northeast North Carolina.

ECU faculty members Qubin Qin, Sean Charles, Stu Hamilton, Coastal Studies Institute research technician Jude Sproul and integrated coastal sciences doctoral candidate Kachapond Chettanawanit conducted research over a six-month span at a coastal restoration planning project on the island.

The refuge, located in Currituck County, was established by the U.S. Fish & Wildlife Service (USFWS) in 1960 to protect migratory birds and their habitat on Knotts Island, which is a wintering area along the Atlantic flyway.

Tundra swans, seen here in January’s snowfall, are one of several bird species found at Mackay Island National Wildlife Refuge. (Contributed photo by Craig Daniels)

The abundance of migratory waterfowl has drawn hunters to Currituck Sound since the time of the Algonquin people. Hunting clubs were a mainstay there from the 1870s. According to the USFWS, Joseph Knapp bought the island in 1917, built a resort and experimented with various wildlife management techniques. Knapp, a wealthy businessman and philanthropist, founded More Game Birds in America, which became Ducks Unlimited. Ducks Unlimited supported the ECU research.

The research team focused part of its work on Corey’s Ditch, a roughly 1-mile channel in Currituck Sound. Originally created with dynamite to improve navigation, the ditch has raised concerns among USFWS and Ducks Unlimited because it may alter local water movement and contribute to erosion along nearby marsh edges. ECU’s role is to help further evaluate this concern by modeling currents, water levels, salinity, bottom shear stress, sediment-movement potential, and transport pathways under different restoration and future-condition scenarios. These processes can remove sediment, weaken marsh stability and accelerate the transition from marsh to open water.

“The modeling does not guarantee that a restoration alternative will produce a specific outcome,” Qin said. “Instead, the scenarios allow us to test how each approach may change water levels, currents, salinity, bottom shear stress and transport pathways under representative environmental conditions.”

To evaluate potential restoration outcomes, the research team used models to compare different management scenarios, focusing on water levels, currents, salinity, transport pathways and bottom shear stress. Bottom shear stress is important because it helps indicate where sediment may be eroded instead of deposited.

Qin added that the goal of the research is to help property managers understand how flooding, water exchange, erosion potential, sediment movement, salinity and marsh resilience may be impacted through different models before real-world decisions are made.

A Beneficial Project

Qin believes the project is beneficial for both ECU and eastern North Carolina.

“It helps ECU by showing how university expertise can directly support real-world coastal restoration and management decisions. It brings together ECU strengths in coastal science, numerical modeling, wetland dynamics and resilience planning.

“For eastern North Carolina, the project is important because many coastal areas face similar challenges: marsh loss, shoreline erosion, flooding, sea-level rise and pressure on roads and other infrastructure. The tools we are using at Mackay Island can help managers evaluate restoration options before construction and better understand the tradeoffs among habitat protection, flood protection and long-term resilience,” he said.

The research gives wildlife managers the opportunity to plan instead of working to develop a solution to a current problem. Qin believes this change in strategy could provide long-term benefits.

“In a broader sense, this research helps shift coastal restoration from a reactive approach to a predictive one. Instead of only documenting marsh loss after it happens, we can compare possible futures and identify actions that may help protect both ecosystems and communities,” he said.

Exploring Options

A component of the research is the fear that Mackay Island is experiencing wetland loss through a combination of erosion from both currents and sediment loss, flooding, ditch

A team of ECU researchers studied marsh loss and erosion at Corey’s Ditch marshland in Mackay Island National Wildlife Refuge. (Contributed photo by Sean Charles)

widening and shoreline exposure. When a marsh can’t keep pace with rising water levels, frequent flooding occurs, which results in weakened vegetation, sediment loss and the conversion of marsh to open water.

“There is concern that these processes are already occurring and may accelerate in the future,” Qin said. “Our project includes both restoration scenarios and future sea level rise scenarios. One scenario represents a case where Great Marsh cannot keep up with sea level rise, while another represents a successful restoration or preservation case where the marsh maintains its current footprint by gaining elevation.”

Using models, the team was able to evaluate how the different alternatives would change water levels, currents, salinity, bottom shear stress and transport pathways. Each scenario represented an entire year of conditions to account for seasonal variability, storms and wind conditions.

Previous preservation actions were focused on a solution that used plugs to reduce excessive flow through Corey’s Ditch. This project explored several options with one goal: to stabilize and rebuild marsh habitat.

“These approaches may influence marsh resilience in different ways,” Qin said. “Breakwaters and shoreline stabilization are designed to reduce shoreline exposure and protect marsh edges, adding culverts to improve water flow across the road and applying thin layers of sediment or creating terraces to help rebuild marsh elevation and habitat within Great Marsh.”

For The Birds

With its location along the Atlantic flyway, Mackay Island offers migratory birds needed habitat for feeding, resting and shelter. A healthy marsh supports a variety of habitats, which in turn attract different species of birds. Bird species found in the refuge include snow geese, tundra swans, mallards, wood ducks, American black ducks, American wigeon, green-winged teal, gadwall, northern pintails, herons, egrets, rails including king rail, bitterns, northern harriers, ospreys and bald eagles.

Restoration options would help birds by preserving the marsh and their needed habitats, while losing the marsh would make the habitat less diverse and could limit bird species.

“The benefit to birds is indirect but important: by improving marsh resilience and reducing erosion potential, restoration can help maintain the physical habitat that birds rely on,” Qin said. “Furthermore, wetlands improve estuarine water clarity by filtering sediments and removing excess nutrients through plant uptake and biogeochemical processes in wetland soil. Clearer water can support submerged aquatic vegetation, which provides important food and habitat for migratory birds, fish and other species.”

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