ONNA RESEARCH + DESIGN
DELFT, NL | WORLDWIDE
COASTAL RESILIENCE PROPOSAL FOR GEORGE LANE BEACH IN WEYMOUTH, MA
Our team of engineers, designers, ecologists and social scientists from around the US was tasked with designing an adequate flood defense system for George Lane Beach, a public beach located in North Weymouth, MA. Plans to raise the height of the existing seawall in response to significant flooding from winter storms are underway, supported by a grant of $129,000 through the state of Massachusetts Municipal Vulnerability Program. In addition to mitigating coastal flood risk, the proposal also needed to protect residents' connectivity to the mainland during storm events and preserve an acceptable degree of public beach accessibility.
ADDRESSING FLOOD RISK IN A VULNERABLE COASTAL COMMUNITY
During a site visit, we used rangefinders to create digital elevation transect, completed a rapid ecological assessment of two salt marsh areas on site, and interviewed Weymouth residents at the beach about their concerns for coastal adaptation. We found they were generally displeased by the idea of losing their beachfront views to a monolithic structure, and are open to alternative plans.
RESEARCH AND ANALYSIS
Together, our team combined insights from the field with climate change projections, coastal morphological conditions and demographic data to produce engineering specifications for an integrated seawall design. We sourced latest estimates of sea level rise in the local area, modeled hydrological conditions including fetch and runup, and considered cost, constructibility, permitting, ecology, site accessibility, and co-benefits to the Weymouth community. Additionally, our proposal suggests holistic strategies to perform construction to minimize social-ecological disruption and CO2 emissions, such as using excavated material from the water-retaining bioswales as fill for the raised road.
KEY PLAN ELEMENTS
Our proposal consists of the following recommendations:
- Raising the height of River Street by converting it to an earthen embankment with a vegetated retaining system to ensure vehicular access in the event of a major storm event;
- Construction of an artificial reef at the northwestern peninsula headland designed to dissipate wave energy and provide new intertidal habitat for the native blue mussel, Mytilus edulis and avoid disrupting an existing eelgrass ecosystem;
- Designation of the parking lot as a stormwater retention area during major storm events to concentrate tidal flooding and protect adjacent property; and
- Increasing multimodal transportation to the beach via a new bus route and bike lane, which allows better connectivity to the Weymouth mainland and the greater Boston area.