Ring’s Island – Coastal Flooding Preparedness

The Ring’s Island neighborhood of Salisbury, Massachusetts lies on the north bank of the Merrimack River near its mouth. Coastal flooding during storms and extreme high tides floods roads and causes damage to homes and businesses due to the low elevation and undersized culverts. Eight to 10 times each year, flooding in the area leaves only one evacuation route, stranding residents and making it difficult for emergency vehicles to reach the neighborhood. Seeking to increase the resilience of the neighborhood, the Town of Salisbury retained the team of Weston & Sampson and Woods Hole Group to help them apply for funding under the Massachusetts Municipal Vulnerability Preparedness (MVP) Action Grant program. Their ultimate goal is to provide preliminary design services to look at raising the elevation of the access/egress roads and improve tidal flushing through culvert replacements.

Once funding was obtained, our team held a kick-off meeting with local stakeholders to discuss the proposed approach, conducted a site visit to review recommendations and project goals, and provided preliminary survey services to tie in the proposed roadway elevations with existing conditions. Future final design services will include simulation modeling to update the previous model and a wind-wave analysis to determine the wave conditions during storm events. We will also determine the needed scour mitigation design on either side of the culvert. Using this information, our team’s final design will involve installing an earthen berm or a concrete block retaining wall to raise the grades of the two main access and egress roads by roughly two to three feet. This will provide added assurance that, during storms and extreme high tides, residents and emergency personnel will have more than one way in and out of the Ring’s Island neighborhood. Our team will also design and permit the enlargement of several culverts under the roads in question to allow additional tidal flushing and preventing the high storm tides from backing up onto the roads and into the surrounding neighborhood.

The use of appropriately sized culverts will also promote re-establishment of a healthy wetland and provide improved aquatic habitat, water quality, and carbon sequestration. The reduction in flooding and associated damage will also reduce clean-up efforts and costs on access roads. The Town of Salisbury to date has received a grant for preliminary and final design of about $400,000 to move forward with the project.

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Posted in Climate Resilience, Geotechnical, Industry-Municipal, Municipal Vulnerability Preparedness, Resilient Design and tagged .