Woods Hole Group Vice President and coastal engineer Bob Hamilton was quoted in a recent article in the Boston Globe on sea-level rise and the status of coastal protection structures in Massachusetts.
In 2009, the state commissioned an inventory of publicly owned sea walls and coastal barriers which found almost 165 structures in need of over one billion dollars in repairs. Faced with rising seas, more frequent and more powerful storms, and budget shortfalls throughout the state, coastal towns must deal with difficult questions and even harder choices.
Sea walls helped shape Massachusetts. As people discovered the joys of hot summer sand and cool ocean breezes, they flocked to build homes in coastal communities. Sea walls went up in the 1930s, ’40s, and ’50s to protect their investments.
It did not take long for property owners down the coastline from sea walls to notice something missing: sand. While the hard structures protect homes behind them, they often lead to erosion of unprotected adjacent properties by interrupting the supply of sand that waves normally move along the shore. In 1978, Massachusetts passed a law that largely prohibited the construction of sea walls or anything like them to protect homes built after that year.
Now, as seas advance, passions are running high on what to do. Many state and local environmental officials acknowledge that letting shorelines loose is the best answer, but they quickly add it is an impractical solution given all the homes, businesses, and roads protected by sea walls. Others say the best protection against rising seas is more coastal defenses, but ones better crafted to work with nature.
“The key here is to have a restored beach for natural storm protection along with hard solutions such as sea walls,’’ says Bob Hamilton of the Woods Hole Group, a private consulting firm that works with coastal homeowners and governments. Yet, he acknowledges this solution is expensive.
Bob is quick to point out that while a seawall may be the most effective way to protect upland property, it does little to nothing for the beach. As the Globe’s diagram shows, without a restored beach in front, sea walls bear the full brunt of wave attack and surrounding sands continue to erode from scouring at the base as well as overtopping. These effects will only intensify as sea level rises. We advocate restored beaches because they provide a necessary buffer for coastal infrastructure as well as habitat and recreational benefits.
As is the case with seawall repairs, money is a limiting factor for beach nourishment projects. In our experience, trucking and/or barging sand from upland sources can range from $20 to $40 per cubic yard, whereas dredging and pumping sand from offshore sources can decrease costs significantly (less than $15 per cubic yard). Unfortunately the regulatory environment in Massachusetts makes offshore sand mining for beach nourishment much more difficult than other states. The Commonwealth has permitted dredging for beach nourishment on a limited basis, and Woods Hole Group has been able to secure these permits on a case by case basis when all environmental impacts have been properly investigated and minimized. What is needed to facilitate beach nourishment projects (and by association upland protection) in the state is new policy, based on a regional sediment management model, which grants access to offshore sand sources and encourages projects to utilize sediments from the local littoral system.
For more information on sea-level rise and sea wall vulnerability in Massachusetts, read the Globe article by Beth Daley: