Castle Neck River Restoration

In 2023, the Ipswich River Watershed Association (IRWA) was awarded federal funding from the National Oceanic and Atmospheric Administration (NOAA) to address coastal resilience. The grant money will be used in part to fund abandonment of Old Essex Road over Castle Neck River through the construction phase, as well as to develop conceptual designs for culvert upgrades at the other two crossings on Castle Neck River: Route 133 and Chebacco Road.

In August of 2023, the Town of Ipswich was awarded a Municipal Vulnerability Preparedness (MVP) Action Grant. The purpose of the MVP Action Grant is to help fund town-led projects that focus on climate adaptation– taking action to prepare for climate change and its impacts, such as extreme weather, sea level rise, and inland and coastal flooding. To learn more about the MVP program, visit the  link  to their website. For the Town of Ipswich and its project partners (the Town of Essex and IRWA), the grant will be used to fund the design and permitting of Old Essex Road, as well as an assessment of alternatives for Route 133, to help guide the conceptual design process.

In the spring of 2024, funding was awarded to IRWA by the MassBays Healthy Estuaries Program for the pre- and post-construction water quality and marsh monitoring at Old Essex Road, which will then be used to develop a framework for monitoring at all three crossings over Castle Neck River.

The Great Marsh in Massachusetts has experienced more frequent flooding in the past 50 years than ever before. In many cases, the flooding has been made worse by outdated and inadequate infrastructure. Per the  Massachusetts Climate Change Assessment , the North Shore is incredibly vulnerable to infrastructural damage from sea level rise, particularly for coastal buildings, roads, and ports.

Castle Neck River is a coastal stream located on the North Shore, with a 2.4 square mile watershed that is primarily tidal salt marsh. The stream marks the border between the towns of Ipswich and Essex, and lies completely within the Essex River/Essex Bay Estuarine Area assessment areas of the MassBays region, as outlined in the  Comprehensive Conservation and Management Plan  (CCMP). The CCMP’s Current Condition of the Bays classified most of the North Shore into the “yellow” ecotype, as the shoreline is more protected than exposed, and is relatively abundant in both sediment and saltmarsh. The report’s habitat goals for this ecotype include increasing acreage for eelgrass, maintaining acreage for salt marsh and tidal flats, and improving water quality across all three habitats. 

Despite being relatively undeveloped, Castle Neck River and its associated salt marsh are significantly affected by man-made barriers– namely, where roads crisscross over the river and the marsh. Both the Old Essex Road culvert and the Route 133 culvert were given a “high” priority in the  Great Marsh Barriers Assessment , based on their constriction of flow. According to a series of site assessments performed by the Massachusetts Division of Ecological Restoration in 2010, the marsh in the project area appears to be degrading over time, with the marsh plain becoming wetter—converting from a high marsh system dominated by saltmarsh hay (Spartina patens), to a saturated marsh dominated by the hydric and stunted form of cordgrass (Spartina alterniflora) and open water pannes.

Roads disrupt continuity of the marsh and restrict natural tidal processes, harming the ability of the marsh to function– especially as habitat for forage fish.  In smaller streams, such as the Castle Neck River, you would expect to find small forage fish, such as mummichogs and silversides, that are prey for larger species, like striped bass and even Atlantic and Short-Nose Sturgeon. However, the Old Essex Road and Route 133 crossings currently discourage the presence of forage fish in the Castle Neck River system, and their predators in the greater Essex Bay system. This project will restore flow of the river and the tides and allow for marsh restoration, which will enable forage fish species to return.

The first phase of the project will address two high priority coastal barriers in an area that is at high risk for sea level rise, storm surge, and extreme precipitation. The MVP grant will enable the Towns of Ipswich and Essex to increase local climate resiliency.

A phased approach to the restoration of Castle Neck River and its salt marsh provides a unique opportunity to collect meaningful and valuable monitoring data pertaining to the MassBays CCMP. The MassBays grant funds will go towards the development of a robust monitoring and data collection plan would allow a site baseline to be established and record how key metrics are impacted by the currently funded restoration work. 

Both the Ipswich and Essex MVP reports have identified the following top hazards: 

• Coastal flooding from storms and sea level rise
• Coastal erosion
• Flooding caused by severe precipitation events, improperly-sized culverts, and other barriers

The project phases will address each of those hazards. 

This project has a high potential to positively impact local communities, specifically for the municipalities of Ipswich and Essex. Although there are no environmental justice (EJ) areas in Ipswich or Essex, both towns are home to several priority populations– these are groups of people who are "disproportionately impacted by climate change due to life circumstances that systematically increase their exposure to climate hazards or make it harder to respond." Explore the slideshow below to see which priority populations are found by the project site.

Route 133 is a state route that runs between Lowell and Gloucester, and goes through the following towns with EJ populations: Lowell, Andover, North Andover, and Gloucester. The specific EJ communities that would be most impacted by this project are those that lie in Gloucester– Route 133 is one of the only main roads out of Gloucester, and many drivers would likely have to cross over Castle Neck River on their commute.

Massachusetts sea level rise projections indicate that both Route 133 and Old Essex Road are extremely vulnerable to sea-level rise. Designing a climate resilient Route 133 crossing and eliminating the Old Essex Road crossing will significantly reduce transportation vulnerability, for both the local priority populations of Ipswich and Essex, as well as the EJ populations serviced by Route 133.

This project can build community capacity for climate resilience by connecting residents’ concerns with larger town-wide vulnerability action plans. Neighbors of the project site were the ones to initially approach the Town of Ipswich about abandonment of Old Essex Road, due to traffic concerns. The project not only addresses their concerns, but it also directly incorporates the top resilience recommendations from each town's MVP report.

The  RMAT Climate Resilience Design Standards (CRDS) Tool  is an interactive web-tool that provides a location-specific climate risk screening and then recommends resilient design standards to guide projects. Using the Tool for the first phase of the project, it was found that the Route 133 crossing at Castle Neck River is expected to be at high risk for sea level rise and storm surge, and extreme precipitation. The crossing at Old Essex Road is also subject to increases in tidal elevation and precipitation depth.

Both the causeways at Route 133 and Old Essex Road are located in FEMA Flood Zone AE (EL 10), meaning that in a given year, there is a 1 in 100 chance of a flood occurring where water elevation will reach 10 feet. Using the  National Map from USGS tool , the elevation of Old Essex Road was found to be 9.55 feet, and Route 133 was 10.76 feet

According to the CRDS tool's projections, at Old Essex Road the tidal datum is projected to reach 9.4 feet. This is right at the base flood elevation threshold, and only slightly lower than the road itself. This means that in major precipitation events or coastal storms, the water level will likely rise above the road and flood it– which can cause major damage to the road and harm to anyone using it. 

Water surface elevation refers to the maximum height of flooding during a 1 in 1000 chance flood event, considering storm surge, tides, and wave heights. In this 0.1% chance flood event, water surface elevation at the Route 133 causeway over Castle Neck River is projected to reach 11.7 feet by 2030, 13.8 feet by 2050, and 15.4 feet by 2070, all exceeding the base flood elevation and the elevation of the road. In that flood event, the causeway will experience extreme flooding– impairing its ability to function, its structural integrity, and the safety of commuters.

So, why road abandonment? Road abandonment stems from the same vein of thought as managed retreat. Managed retreat was a term coined only several decades ago, but has been a concept in practice for over a hundred years. Generally speaking, it involves the purposeful movement of people and infrastructure away from risks. In regards to climate change, managed retreat is most often associated with sea level rise. It is a relatively newly recognized coastal management strategy, which allows for human development to be “moved” out of harm’s way while natural coastal habitats are subsequently restored in order to act as a natural buffer against flooding. Basically, managed retreat allows the shoreline to move inland, instead of trying to “hold the line” with structural engineering. Both managed retreat and road abandonment, despite their connotation, are not the same as giving up. They are simply additional tools to use towards climate adaptation and mitigation.

The upper Castle Neck River is one of the most flow restricted and impaired saltmarsh areas in the entire Great Marsh. Restoring the natural flow of water in this river system – through road abandonment and stream restoration, two top-tier nature based solutions – will significantly improve the marsh's ability to repair itself. Nature-based solutions are those that incorporate "natural features or processes into the built environment to promote adaptation and resilience" ( FEMA ).

Marsh restoration promotes marsh migration, which is crucial for the long-term health of the Great Marsh and its resilience to climate change. Marsh migration is the conversion of neighboring inland habitats into marshlands– it is a natural process that happens in order to allow salt marshes to survive in the face of sea level rise.

The project will directly create over 5,000 square feet of new salt marsh where the southernmost stretch of Old Essex Road currently sits.

Completion of this project will result in substantial environmental benefits including improved water quality and flow, restored bird and fish habitat, and carbon sequestration. The project will also improve fish migration within the marsh and to upstream freshwater streams for migratory species.

Climate change is not confined to town boundaries, and its wide-reaching impacts necessitate the need for regional action. The Castle Neck River Restoration Project came as a result of many regional studies and research efforts: The North Atlantic Aquatic Connectivity Collaborative stream continuity database, The Great Marsh Barriers Assessment, the MassBays CCMP, and the Parker-Ipswich-Essex Rivers Restoration Partnership ( PIE-Rivers ) stream continuity action plan.

This project will not only reduce local transportation vulnerability, but it will increase the resilience of a state road that services nine towns across two counties. The proposed marsh restoration at these sites will benefit the Great Marsh as a whole, including all eight towns in the Great Marsh.

This project will be readily transferable to the 29 municipalities that are in the PIE-Rivers region, especially the coastal communities where this type of work will be increasingly common. As one of the first-ever road abandonment projects, it will serve as an example for all communities across the Great Marsh of a project designed specifically to reduce climate vulnerability and restore habitat connectivity in the Great Marsh.

Although rarely implemented, road abandonments are becoming increasingly pertinent for communities in the Great Marsh with road crossings that are susceptible to sea level rise. Infrastructure abandonment is often a difficult conversation to have with residents and stakeholders, so having a case study to point to is invaluable for future discussions.

Pre-restoration monitoring for Old Essex Road will begin in July 2024, and extend through summer 2025, when implementation is set to begin. During the pre-restoration monitoring phase, several continuous loggers will be placed at the site. The loggers will measure pressure (depth), temperature, salinity (specific conductance), and dissolved oxygen. There will also be discrete monitoring conducted with a handheld meter measuring dissolved oxygen, temperature and specific conductance on a monthly basis. Discrete monitoring will be done on both the eastern and western side of the current Old Essex Road causeway.

Citizen scientists will also perform a pre-restoration vegetation survey in order to establish a baseline extent for the existing marsh. After the road removal, these vegetation surveys will continue to track marsh migration.

Early on during pre-restoration, fish sampling will occur as an educational and outreach event. Sampling will occur upstream and downstream of the Old Essex Road crossing. 

Towards the end of the pre-restoration monitoring phase at Old Essex Road, IRWA will start planning for how future pre-restoration monitoring would look at the two other crossing sites, adapting for site-specific conditions and making adjustments based on what we learn at Old Essex Road. Part of the planning process will include writing up a Best Management Practices (BMP) for pre-restoration monitoring, so that there is an easily accessible framework guide available for those future projects. A BMP will also make this project transferable to other embayments and ecosystem problems, specifically those relating to water quality issues.

While the Old Essex Road crossing removal and abandonment occurs, IRWA will prepare for post-restoration monitoring. While most of the pre-restoration monitoring methods will be kept in place post-restoration, there will be additional monitoring to supplement the pre-restoration regime– mostly in regards to measuring marsh migration. 

During construction in summer 2025, the continuous loggers will remain in place, in order to record any major disturbances to water quality (even though this should not happen, as measures will be put in place to minimize construction impacts to the surrounding environment). After construction is complete at the end of summer 2025, the continuous loggers will continue to record pressure, temperature, salinity, and DO. Discrete monitoring will resume on a monthly basis, with the addition of performing vegetation surveys as indicators of marsh migration. Once the culvert and roadbed is removed, we hope to see marsh restoration via the water quality metrics and vegetation surveys. 

For long-term post-restoration monitoring after December 2025, the continuous loggers will remain at the project site to measure water quality. Discrete water quality and marsh migration monitoring will continue on a monthly basis, as well. Another fish sampling event will take place in summer 2026. Although fish are very mobile and sampling will not be used as an official metric of success of restoration, it will be informative to repeat the event under similar conditions post-restoration and see if there are any notable changes.

During post-restoration monitoring, IRWA will start to plan for post-restoration monitoring at the other two crossings in the future, as well as the broader monitoring framework that will be established all along Castle Neck River after the completion of all three restoration projects. The BMP will be updated with the short- and long-term post-restoration monitoring framework.