The Army Corps of Engineers on Thursday released the preliminary report for its study on New Jersey’s back-bay flooding, and it contains some multi-billion dollar engineering projects.
Under consideration are storm surge barriers in the Great Egg Harbor and Absecon inlets.
The moveable gates would stretch across the mouths of the inlets and close during storms to prevent water from entering the bays and inundating nearby homes.
Of 3,400 miles of shoreline, such barriers “are viable options at Manasquan Inlet, Barnegat Inlet, Absecon Inlet and/or Great Egg Harbor Inlet,” according to the report. The Hereford Inlet and Brigantine Inlet were ruled out for being costly compared with the benefits it could provide.
“We look at the costs and benefits. ... Is the cost of building the structure less than the benefits?” said J.B. Smith, an Army Corps project manager.
Storm surge barriers are multi-billion dollar engineering feats, and funding for the Army Corps’ ideas is not in place yet.
One built in the Netherlands in the 1990s, called Maeslantkering, is controlled by a supercomputer and automatically shuts when flooding is imminent. It took six years to build and cost 450 million euros. The Army Corps has proposed a similar storm surge barrier in New York City.
The report also says higher floodwalls or levees are feasible in Cape May, Wildwood, Sea Isle City and a number of other shore towns. Floodwalls, more effective than bulkheads for flood reduction, could be built three to five feet higher and deeper into the ground, Smith said.
There are drawbacks to that though. Building floodwalls close to homes can be difficult and may hurt views of the bay.
“One of the cons for flood walls is they have an impact on aesthetics. ... And some of the construction is complicated in the vicinity of houses,” Smith said.
The New Jersey Sierra Club opposed the report’s suggestions for hard structures like floodwalls and storm surge barriers that may greatly alter natural habitats.
The organization prefers other flood mitigation strategies outlined in the report, including living shorelines, wetland restorations and retreating from barrier islands.
“(Seawalls and gates) will stop the flushing of Bays and tidal areas, keeping pollutants trapped such as toxic sediments,” the group’s president, Jeff Tittel, said in a statement.
The preliminary report identified general environmental impacts but said quantifying the effect on animals and wetlands would be difficult at this early stage in the study.
Floodwalls and levees may lead to habitat loss at wetlands and submerged aquatic vegetation, according to the report. Storm surge barriers could significantly impact tidal flow, tidal range, water quality and flora and fauna.
“A detailed examination of impact avoidance and minimization to better quantify both direct and indirect environmental impacts will also be performed in the future,” the report says.
The study, launched in 2016, is one of the first steps in the Army Corps’ decades-long look into how to ease bay flooding, where there have historically been fewer investments compared with the oceanfront. The public weighed in during meetings last year in Ventnor and Toms River. Further analyses need to be completed and funding from Congress secured, so the earliest that construction could begin is 2030.
The cost of the study is being shared by the Department of Environmental Protection and the Army Corps.