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12/06/2017 08:45 AMHow much the sea will rise is uncertain, but change is
coming, and both the town and its residents should get prepared. That’s the message to the town and its residents from GZA Environmental, delivered in a Nov. 15 presentation of its Coastal Resilience and Sea Level Rise study findings.
“Part of our mission here is to create an educated citizenry that will leave with an understanding of the challenges and of the science,” said GZA Senior Vice-President and principal Dan Stapleton.
The GZA study was funded by a $125,000 planning grant the Town of Old Saybrook was awarded by the state in January 2016.
The town’s website www.oldsaybrookct.org states the study would “provide a detailed assessment of the risks from sea level rise with respect to community assets including coastal infrastructure, essential facilities and structures, neighborhoods, natural and recreational resources, and other critical town-owned assets...and...help the town develop resiliency strategies and adaptation actions to mitigate or reduce risks to vulnerable areas.”
To complete a town vulnerability assessment, GZA began by studying existing conditions and collecting and mapping information on areas already subject to tidal flooding, those that experienced extreme flooding during the major storm events of Irene and Sandy, and those that face increasing risk of flooding as sea level rises.
Setting a Baseline
GZA began by defining terms. The first term was “chronic inundation,” or flooding that occurs 26 times per year over 10 percent of a town’s land.
“That’s not going to be the driver over all of Old Saybrook, but communities within Old Saybrook may face that,” said Stapleton.
Though town neighborhoods do not yet flood 26 times per year, streets like Great Hammock Road near the Town Beach and streets in neighborhoods like Chalker Beach do flood from time to time. This flooding mainly occurs now at high tide during astronomically driven events like a full moon and during storms with high winds that drive water into the coastline and the town’s marshes.
The second term, “extreme flooding,” is a condition that occurs during major storms like Tropical Storm Irene and Superstorm Sandy, Stapleton said. Extreme flooding layers storm surge above the mean sea level line and wave action on top of an area’s normal mean sea level.
Any mean sea level rise would be likely to increase the likelihood and severity of chronic and extreme flooding events in vulnerable areas.
So then Stapleton reviewed the current 2017 projections for sea level rise offered by the Army Corps of Engineers (USACE) and by the National Oceanic and Atmospheric Administration (NOAA). According to USACE, by 2040, the mean sea level in the area could rise between .05 and 1.23 feet. NOAA projects a higher likely sea level rise of approximately 1.1 feet by 2040.
Even small changes in the current sea level would increase the severity and intensity of future flooding—in major storms, four- to six feet of wave action would be layered on top of the then-current flood elevation line.
Areas of Concern
In evaluating Old Saybrook’s essential facilities, GZA found that most of them are not vulnerable to sea level rise. The Town Hall, schools, the Old Saybrook Ambulance facility, and the Police Station are all located at higher elevations.
“The town’s physical structures are quite good. The risk to structures is not bad. The biggest issue is that they can’t perform their mission south of Route 1” in the event of extreme flooding, said Stapleton.
The reason is that, although ambulances and police vehicles could leave their headquarters, roads like College Street and the causeway at Saybrook Point would be inundated by flooding, so emergency responders would not be able to use the roads to get to people in need of help or evacuation.
Addressing the Risks
To address that risk, GZA’s Sam Bell presented a list of strategies the town could use to increase resiliency and adapt to the coming changes in sea level. First would be to create a Town Coastal Resilience Team charged to monitor and coordinate town efforts to adapt; second would be to identify and prioritize proposed projects; third would be to create a Resilience Project Fund to finance the highest-priority projects; fourth would be to create a resilience permit compliance plan; and fifth, to incorporate the resilience study results in the town’s 2019 Hazard Mitigation Plan and in the Town Plan of Conservation and Development.
“[The approach] is more about adjusting to living with water, like the Dutch do,” said Stapleton.
To accommodate, the town could pursue measures like elevating structures and possibly roads and infrastructure, and where possible, create a living shoreline (in which sand dunes are stabilized by native vegetation.)
In all the strategies, the town will need to determine its appetite for risk.
“What levels of flooding do you want to protect against?” Stapleton asked.
Making accommodations to a future with more water and flood risk may be the best strategy for the town and homeowners to pursue, Stapleton said.
To protect at-risk homes from future flooding, perimeter protection is one option. An example of this would be to build a 13- to 15-foot levee around the edges of a homeowner’s property. While this would not lower a homeowner’s insurance premium, it still could protect a home from flood damage.
Other accommodations could include widening beaches to create dunes or creating a living shoreline, like a pilot project in Fenwick is designed to do. These approaches are very effective in a normal environment, according to Stapleton, but would not provide protection in a major storm.
Ultimately Stapleton said an important accommodation to adapt to sea level rise in Old Saybrook would to adapt the town’s emergency response equipment and mission to a future with more chronic or extreme flooding.
“I think this is the future,” said Stapleton.