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06/20/2017 05:45 PMHow would the town’s municipal infrastructure and residential neighborhoods be affected by sea level rise projections for 2040? For 2065? Or by 2100? Last week representatives of GZA Geoenvironmental offered answers to these questions in a community presentation of its findings so far in this grant-funded Sea Level Rise study. A final report and presentation of findings will be in September.
Risk of flooding in storms or in extreme tides is a situation faced by many properties south of Route One since much of the land is just six, seven, or eight feet above the still water elevation. In the future, any increase in the average sea level would begin to affect these properties and the town roads more often than today.
How much will the sea level rise? That depends on which projections are selected. For the purposes of this study, GZA said it used the Army Corps of Engineers and National Oceanic and Atmospheric Administration’s (NOAA) projections. For the year 2040, the sea level rise is projected to rise between 0.05 and 1.23 feet compared to today; for 2065, between 0.24 and 2.96 feet.
According to Dan Stapleton of GZA, there is already documented and measurable sea level rise in recent history near the Town of Old Saybrook.
Over the past 80 years, Stapleton said, the New London Tide Gauge has recorded a sea level rise of about 1 mm per year. Could this historical sea level rise accelerate in the next decade? Some environmental factors such as evidence of an increased Arctic sea ice and Greenland ice pack melting suggest this is a possibility; in 100 years, this could mean an increase of about one foot.
Identifying how towns like Old Saybrook can plan for a future that’s so uncertain is a challenge.
First, the town has to identify and quantify areas and facilities at risk. This is the goal of the GZA study, to take stock of the town’s essential facilities and infrastructure; weigh their location and elevation against projected sea levels in 2040, 2065, and in 2100; and assess the vulnerabilities to flooding and damage.
Sam Bell of GZA said that so far, the firm has completed a inventory of town assets and characterized the coastal hazards. (For those concerned about possible consequences of their property’s appearance in the report, Bell noted, “We’re doing a study, not a plan, so it has no regulatory impact. FEMA makes flood risk maps.”)
Bell said the good news for the town is the town’s “essential facilities,” defined as the police station, fire station, ambulance facility, official storm shelter (for Old Saybrook, the Old Saybrook High School), and Town Hall are all at low risk of being affected by sea level rise, due to their location and elevation.
“The bad news is that the town’s roadways are at risk and can be inaccessible and lifeline facilities [like septic systems] would face a significant impact from sea level rise,” said Bell.
Bell and Stapleton displayed several maps that showed how sea level rise would affect the community in 2040, 2065, and 2100. In the worst-case scenarios, upland areas become almost like islands in the midst of flooded wetlands, with access roadways underwater or subject to periodic tidal flooding.
“At a 100-year flood, you’re completely isolated,” said Stapleton.
As the sea level rises, “roads in beach communities would flood all the time. The ambulance isn’t any good if you can’t get anywhere,” Stapleton continued. “We’re trying to look at options to maintain a coastal resiliency corridor, to keeping road access along that east-west and north-south axis.”
The east-west corridor to which he referred roughly follows the Boston Post Road/Route One path and the north-south corridor, College Street section from Main Street to Saybrook Point.
“In 50 to 60 years, a three-foot sea level rise is a reasonable estimate. Wetlands that now flood irregularly will regularly flood. At 100 years and a five- to six-foot sea level rise, wetlands would become waterways. Over time, the town would lose irregularly flooded marsh and gain more regularly flooded marsh,” said Bell. “Wetlands tend to attenuate waves, so the presence of wetlands will knock down waves—but they also will let the storm surge in.”
GZA studied six neighborhood areas to assess the respective risk of sea level rise to these areas: Otter Cove/Ayers Point, Route 1-Ferry Point, Connecticut River Ragged Rock Tidal Marsh, Low beach communities like Chalker Beach and Plum Bank, Saybrook Point-Town Center South, and Cornfield Point to Fenwood.
GZA has scheduled neighborhood workshops to again present their findings and discuss them with community members; the first was on June 20 and the next will be on Tuesday, Aug. 1. A final GZA report due in September will build on this risk assessment to list actions the town could consider to reduce or mitigate the risk to people and property, given sea level rise scenarios. Another public meeting on the final report is planned for September.
Town Planner Christine Nelson told the packed Duffy Pavilion that the town would upload the GZA presentation and report to the town’s website when available. Residents will be able to find it under the tab/heading for Initiatives.
Editor's note: An earlier version of this story stated that a documented 1 mm annual rise in sea level would result in a rise of one foot over 100 years; the one-foot rise estimate is based on documented and projected increases in the rate of sea level rise.