The Town of Manchester-by-the-Sea experiences frequent flooding from inland and coastal sources. This is due to a combination of hydraulic restrictions from culverts and dams, increased stormwater runoff volumes and rates from impervious developed areas, a highly channelized stream system, poor infiltration conditions, high tides, wave action, and storm surge. Over 75 percent of the Town’s critical assets (including water and sewer treatment facilities, and emergency service buildings) are vulnerable to flooding due to location and elevation. Flooding and water quality problems will be magnified in coming years due to climate change related increased frequency and duration of storms and sea level rise. The Town had a currently approved FEMA Hazard Mitigation Plan (HMP), but this plan did not address flooding due to climate change.
With funding from two FEMA Pre-Disaster Hazard Mitigation (PDM) grants, Tighe & Bond assisted the Town with characterizing flooding impacts from sea level rise, storm surge and extreme precipitation, and their potential effects on critical sectors of the Town. The resulting vulnerability and risk assessment provided the basis to develop mitigation strategies for a five-year update of the Manchester HMP.
The project was coordinated with a concurrent Coastal Zone Management Grant integrating modeling, public outreach, and education component of the grants. A robust public outreach program was coordinated with the Town’s grant administrator and the Manchester Coastal Resiliency Advisory Group representing local, state, and federal stakeholders. A few of the task highlights are presented below.