Restoration Resource Center USA: Maidford River Saltmarsh Restoration: Middletown, Rhode Island

Hanging Rock at Maidford Marsh. Credit: Center for Ecosystem Restoration, RI

Overview

Saltmarshes are arguably one of the most productive ecosystems on the planet, as these areas provide nurseries for birds, invertebrates and a diversity of fish species. Almost 70% of commercially fished species in Rhode Island rely on saltmarshes for at least a portion of their lives.⁹Marshes have a natural ability to both vertically and horizontally accrete over time by collecting sediments, minerals and plant matter.¹⁰ Unfortunately, sea levels are rising faster than marshes can accrete. Saltmarshes are becoming flooded more frequently and for longer periods of time. This has degraded many of these essential ecosystems around the world.

The Sachuest Point Wildlife Refuge in Middletown, Rhode Island spans 247 acres and provides the public with a visitor’s center, hiking trails and scenic overlooks. The Maidford River Saltmarsh accounts for 11 acres of the refuge’s 47 acres of marshlands.⁵. The marsh suffered dramatically as a result of sea level rise and powerful storm surges, with significant degradation occurring during Hurricane Sandy in 2012. The restoration was fortunate to receive funding under the Disaster Relief Appropriation Act of 2013 which was enacted to fund restorations relating to damages caused the storm.

Quick Facts

Project Location:
Middletown, RI, USA, 41.5218243, -71.28345380000002

Geographic Region:
North America

Country or Territory:
United States of America

Biome:
Coastal/Marine

Ecosystem:
Estuaries, Marshes & Mangroves

Project Lead:
U.S. Fish and Wildlife Service

Organization Type:
Governmental Body

Project Partners:
Project partners include: The Nature Conservancy, The Center for Ecosystem Restoration, The Town of Middletown, RI, The Norman Bird Sanctuary, and the Aquidneck Land Trust.

Location

Project Stage:
Post-Implementation Maintenance

Start Date:
2015-05

End Date:
2019-05

Planning \ Design:
6

Implementation:
24

Post-Implementation Maintenance:
12

Monitoring & Evaluation:
6

Primary Causes of Degradation

Climate Change

Degradation Description

The primary cause of degradation of the Maidford Marsh is sea level rise caused by climate change. Strong storm surges during Hurricane Sandy in 2012 devastated an already struggling ecosystem. During the storm, the marsh became heavily eroded and flow channels became blocked causing the marsh to flood more frequently and for longer time periods, especially during rain events which decreased the marshes salinity. This flooding drove out marsh fish, attracted mosquitos, diminished native grass populations and allowed for invasion by Phragmites australis. Secondary sources of degradation include water pollution from stagnant pools and nearby roads.

Defining the Reference Ecosystem

The reference ecosystem is based on diverse sources of information (e.g. multiple extant reference sites, field indicators, historical records, predictive data).

Reference Ecosystem Description

Saltmarshes serve a vital role in Narragansett Bay, providing habitat, nourishment and nursery for terrestrial and aquatic species. They also provide a buffer for upland areas against the winds and waves of storms⁸ and when functioning properly can filter metals and toxins from the water. Originally, the Maidford Marsh was comprised of a mixture of native high and low marsh plants such as Spartina aterniflora, S. patens, Distichlis spicata, and Juncus gerardii. The high marsh grasses at Maidford Marsh had supported nesting populations of the salt marsh sparrow and the marsh as a whole was able to host a variety of migratory birds before degradation.

It is important to note that the Maidford Marsh has not always flowed into the Sakonnet River. Originally, the marsh flowed into Sachuest Bay and was diverted to the Sakonnet River in the 1880’s for construction work.³ This means that the marsh channel is completely manmade. There are currently no plans to redirect the marsh channel back to its original direction because of existing roads.

Project Goals

The main goal of the Maidford Marsh restoration was to improve its resiliency against sea level rise and strong storm surges. Raising the marsh height by thin layer deposition has a cascade of positive effects. Because the marsh was too low to drain at low tide, particularly after heavy rain events, increasing its height improved habitat for native marsh grasses and restored salinity to exclude invasive P. australis. The return of native marsh grasses will restore necessary nesting habitat for the endangered saltmarsh sparrow. In restoring the flow, the marsh will be less susceptible to flooding and formation of stagnant pools. This will improve overall water quality and eliminate habitat for breeding mosquitos.

Monitoring

Monitoring Details:
Monitoring planned once project is completed includes: water quality monitoring (before, during and after storm events), salinity measurements, tracking marsh accretion, vegetation abundance and community mapping, nekton surveys and invasive control.1 Monitoring has not yet begun.

Stakeholders

Middletown residents were the primary stakeholders in the Maidford Marsh restoration. Much of their drinking water is provided by the Maidford River.¹⁴ Poor water quality also caused beach closures due to the outlet of the Maidford River channel draining bacteria-ridden water into the Sakonnet River at Third Beach. This would surely upset any patron trying to get to the beach to cool off with a swim during hot and humid summer days.

Description of Project Activities:
The first segment of the marsh restoration involved a thin layer deposition that added sediment to the top layer of the marsh. This action mimics the marshes natural ability to elevate gradually over time. Sea levels are currently rising almost twice as fast as marsh accretion rates.5 The addition of sediments to the marsh makes up for lost accretion time and gives the ecosystem a chance for success as sea levels continue to rise. Sediment addition ranged from one inch to one foot depending on location with a total of 11,000 cubic yards of sediment added.7 (EAC: 1,2,4) Once the thin layer deposition was performed, flow and drainage was restored by digging out existing channels and creating shallow channels, called “runnels”. This restoration of natural flow is expected to aid in the marshes ability to properly flood and drain during tidal events. This will also eliminate the formation stagnant pools that previously formed after storms. Freshwater flows were diverted to improve the marshes salinity, thus removing habitat for breeding mosquitos and recreating habitat for native fish.1 (EAC: 2, 3, 5, 6) Invasive species management was another important part of the restoration. Phragmites had heavily encroached on the high marsh, replacing native grasses and impeding proper drainage. Phragmites control involved the licensed application of the pesticide glyphosate. Glyphosate was applied to Phragmites in the late summer months when the plants were in full bloom.1 2-4 weeks after glyphosate application, Phragmites was mowed to remove dead matter and reduce shade to allow for native grass reestablishment.1 (EAC: 1,3,5) Native grasses plugs were planted after the deposition in the high and low marsh areas between April and June of 2016.1 S. alterniflora (smooth cordgrass) plugs were planted in areas that experience daily submersion. “Smooth cordgrass is an effective soil stabilizer used on interior tidal mudflats, dredge-fill sites, and other areas of loose and unconsolidated soils associated with marsh restoration.”13 The smooth cordgrass should reduce the erosion rate due to tidal flux. It is estimated that about 22,000 grass plugs of various native species were planted.6 Plugs were planted with the help of local volunteers from Save The Bay, employees from a local CVS Pharmacy, high school students, and many others.6 (EAC: 2,3,4)

Ecological Outcomes Achieved

Achieve a desirable species composition:
Although the restoration is still in progress and has not yet been monitored, it appears that many goals of the project have been achieved. The high marsh is flooding less and the marsh in its entirety drains more easily than before (EAC: 2). Water quality has benefited due to the improvement of drainage. Areas that previously hosted mosquito larvae now appear to be hosting fish populations3 (EAC: 3). The grass plugs planted have thrived in the absence of Phragmites, which will reintroduce nesting habitat for the salt marsh sparrow and maintain the stability of the marsh (EAC: 3,5,6).

Factors limiting recovery of the ecosystem:
Although the marshes functions have been vastly improved, the mouth of the river channel continues to be blocked by sand despite restorationists best efforts to resolve the issue. The thought is that because the river channel is manmade and was created in a beach area, the channel has a natural tendency to be sandy.3 This causes the mouth of the channel to frequently become blocked. The US Fish and Wildlife service is currently working on a plan to resolve this issue with their restoration partners.3

Socio-Economic & Community Outcomes Achieved

Economic vitality and local livelihoods:
Restoration of the Maidford Marsh has improved water quality, removed breeding habitat for mosquitoes and in turn has benefited human safety. West Nile Virus and Eastern Equine Encephalitis have become more prevalent in Rhode Island in recent years.1 Eliminating these mosquito breeding areas has lowered their total production, sequentially decreasing potential for infection. In previous years, pollution from the marsh resulted in closures at Third Beach. Stagnant water from flooding and lack of proper drainage gave mosquitos an ideal breeding location. Flushing the existing marsh channels and increasing ditches to allow salt water to flow more freely eliminated this issue.2

Key Lessons Learned

The restoration displayed a positive response from both terrestrial and aquatic species. Fish and invertebrates seemed to be the first to respond, as they were able to take advantage of improved conditions quickly.¹² Marsh plants are slower to respond, but seem to be progressing on the trajectory of an undisturbed marsh site, although it may be decades before the marsh vegetation becomes fully established.¹²

Long-Term Management

Monitoring planned once project is completed includes: water quality monitoring (before and after storm events), salinity measurements, tracking marsh accretion, vegetation abundance and community mapping, nekton surveys and invasive control.¹

Sources and Amounts of Funding

The Maidford Marsh restoration was funded by the federal government under the Disaster Relief Appropriations Act of 2013. The project was awarded 644,000 US dollars.

Other Resources

Case Study Author: Sophie Clode

USA: Maidford River Saltmarsh Restoration: Middletown, Rhode Island