STONE HARBOR - Stone Harbor Council, during its Sept. 15 meeting, discussed borough flooding issues.
The focus on flooding began with a report from Dr. Stewart Farrell, of the Stockton University Coastal Research Center (CRC). Farrell and his team have been engaged in a two-year study of nuisance flooding in several coastal communities, including Stone Harbor.
As he noted in the written report he supplied to the council, “On many of New Jersey’s barrier islands, low elevation roadways appear to be flooding more than in the past decade.”
Nuisance flooding is becoming more than a nuisance, and local municipal governments are trying various strategies to combat it.
Over 18 months ago, the CRC installed water pressure valves in 16 borough locations. The devices continuously record the presence or absence of water pressure in ways that allow CRC scientists to measure the presence and depth of flooding, as well as its duration.
Farrell reported certain areas of the borough, closest to the bay, are experiencing repeated flooding events not necessarily associated with heavy rains.
The devices recorded up to 328 flooding events, depending upon the location of the sensor. The water depth varied greatly, ranging from 0.17 and 3.10 feet, with an average duration of one to four hours. Many of the events were associated with higher than predicted tides.
Farrell pointed to the fact that the high ground in Stone Harbor is just behind the dunes, with the island sloping downward as it moves to the bay. Bayside flooding, Farrell said, will continue to be the central problem in most borough flood events.
He said several factors influence the frequency and severity of flood events. Among them, he focused on site elevation, celestial alignment, wind direction, and rainfall.
Noting that the mean tide range in this part of New Jersey can vary by 1.5 feet depending on celestial alignment every two weeks, Farrell also warned that rising sea levels will exacerbate the problem.
All of the variables Farrell identified are areas of strategic concern for communities like Stone Harbor. Raising low-lying roadways may be a necessary component of any future strategy dealing with combating rising sea levels and more frequent significant rain events.
Farrell acknowledged drainage and pump systems as a way of dealing with rain event induced flooding.
The next agenda item was a status report by Engineer Thomas Thornton, of Mott McDonald, on a multimillion-dollar project to redevelop drainage systems for a large swath of the island west of Third Avenue to the bay.
The project involves a new stormwater pump station at 93rd Street, as well as enhanced drainage piping throughout a designated area, with an outflow of water discharged into the bay, at 93rd Street.
The pump station will have three pumps, along with a dedicated generator. Water collected from the drainage area moves to a wet well at the pump station, is filtered to remove debris, and is pumped through a new water main down 93rd Street to the bay discharge location.
Concerned that some of the construction of the draining piping may require state environmental permits, which could delay construction of the pump station, Thornton proposed splitting the project and allowing construction of the pump station to go to bid this calendar year. A contract for the street piping could follow. Council was inclined to follow that strategy.
The pumping station design was predicated on expectations of certain levels of rain events.
The borough adopted a series of policies to combat island flooding, ranging from high bulkhead mandates to dune management to pump station construction, yet the threat also continues to expand.
Farrell’s report contained the statement that, “If predicted sea levels of 3.0 to 4.5 feet higher than today do become a reality by 2100, the worst nuisance flooding of today becomes the normal high-tide flooding twice every day.”
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