CAMBRIDGE - Cambridge residents concerned about stemming the increasing tide of flooding packed Dorchester County Public Library meeting room Wednesday, Aug. 21.
Hosted by Make Cambridge Resilient Project Manager Larry Smith, the community meeting to kick off the Flood Mitigation Phase I Design featured Coastal Engineer Anna Johnson and Senior Project Manager Megan Barniea of Bayland Consultants and Designers, the city’s chosen contractor.
The experienced Bayland team has been exposed to a wide variety of site conditions that can impact construction techniques and equipment for successful implementation. “We will develop a construction approach based on actual site conditions,” Barniea said. They also base designs on materials locally and readily available to cut costs and time, she said.
Their design foundation will be based on three main elements of the Shoreline Flood Reduction Plan on the Make Cambridge Resilient website-- the living shoreline, earth and rock embankments, and stormwater management.
“The purpose of the living shoreline is to knock down wave energy and flows to protect the embankments, the first line of defense,” Johnson said.
“Earth and rock embankments will form the flood barrier around the shoreline, from higher elevation on one side of the shoreline to the other, protecting the entire city," Barniea said.
The first step in the stormwater management component will include upgrading the existing storm drain system, which, as Smith said, is older and not able to handle even some current storm events, let alone future storm events, “so we’ll look at upgrading, whether increasing pipe size or having multiple pipes in parallel,” Barniea said.
They’ll also explore using city park spaces as above or below-ground stormwater retention areas. “Between system upgrades and retention areas, that takes the water off of the roadways and properties and stores it underground; when that storage fills up, pumping stations will kick on, moving the water into the river,” she said.
Finally, backflow preventers at the shoreline will keep tidal waters from backflowing up into the storm drain system, Barniea said.
Professor Ming Li of the University of Maryland Center for Environmental Science, supporting the city’s flood mitigation design efforts, provided an overview of how warmer temperatures, leading to increased rain, and rising sea levels, necessitate an innovative approach to future planning, using models into 2050 and 2100.
Li led the group through a series of slides detailing the data behind why “old ideas” like sea walls, built to heights thought to protect coastline property, are no longer viable given current climatic conditions.
“All around the world, the oceans are warming, storms are getting stronger, bringing a lot more rainfall, a trend continuing into the future,” he said.
A growing trend is finding nature-based solutions to manage the risks, he said, pointing to a wealth of scientific data showing that wetland seagrass and oyster reefs creating friction have helped dissipate destructive wave energy.
Smith mentioned that in order to address the broader stormwater management problem, the team is also looking at developing green infrastructure to help absorb it, rather than depending solely on “this grey stuff.”
One example, still a concept design, would be using Gerry Boyle Park to store stormwater temporarily during an event. “It would seep through the ground, then filter out all the contaminants before being discharged into the Choptank, a win/win,” Smith said.
During the question-and-answer period, several people cited concerns about whether pumping stations would be above or below ground, and how planned structures would affect their access to personal watercraft and piers.
Resident Lou Hyman asked whether Bayland consultants had included in their analysis “the flood that happened a week and a half ago, a unique situation where we had severe flooding without rain, with hurricane winds were blowing the water back upstream so we had a high tide that could not go down, then a second high tide on top of it, and we ended up with a foot and a half of water on Water Street, because I measured it, I was out there standing in the middle of it,” he said.
“I do commend the city, because they’ve started doing the repair work on the sewage system, and by doing that they’ve actually tremendously reduced the problems we were having. Just in that first stretch, the water inundating Water Street during the recent flooding was clear,” Hyman said.
In a recent press release, Cambridge City Engineer Bucky Jackson, also at the meeting, wrote:
“The phased project is intended to extend from just west of the city limits, near Gerry Boyle Park, to the mouth of Cambridge Creek, with FEMA is currently funding Phase I Design and Permitting for $1.7M while reserving $16M for Phase II Construction under the FEMA Hazard Mitigation Assistance Grant.”
Jackson disclosed that Bayland’s field surveyors have begun conducting a hydrographic survey measuring tidal information and other physical features including the shape of the shoreline, currents, and water properties. The surveys will be conducted completely by boat in tidal state waters along the Choptank River shoreline.
Based on the project roadmap timeline, the 30 percent milestone should be nearing completion in early 2025, when another public meeting will take place.
For more information and to take the public survey, visit https://www.makecambridgeresilient.org.
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