Sandbags are used to slow the erosion of the bank along the Delaware River.l
Bill Barlow reports for WHYY:
New Jersey’s East Point Lighthouse at the mouth of the Maurice River has survived pelting winds, driving storms and long periods of neglect in its 170 years.
Before the end of this year, a state project could help protect the historic building on the Delaware Bay from eroding land and rising seas.
The state plans to install 900 feet of Geotube, made of flexible material filled with sand, to protect the lighthouse and its sandy bayfront parking lot from tide-driven floods.
The bids will go out soon, with the work to begin in late summer, said Larry Hajna, a Department of Environmental Protection spokesman. That will avoid interference with breeding horseshoe crabs or the migrating birds that depend on their eggs. Once completed, the Geotube will be covered with sand to resemble a dune, Hajna said.
“Basically, it’s a big Christmas stocking which you stuff full of sand,” said Stewart Farrell, the director and founder of the Coastal Research Center at Stockton University in Pomona.
But what’s right for the Delaware Bay may not always be what’s right for a town facing the ocean.
“The East Point Lighthouse is in an entirely different environment than, say, Atlantic City’s Boardwalk,” Farrell said. “What would be fine for the lighthouse would be a complete waste of money out on the oceanfront. Are you trying to stop a runaway freight train? Or are you trying to stop a kid on a bicycle?”
Several factors determine waves. The strength of wind blowing across the water and the area of water surface over which that wind blows — known as fetch. It’s a little over 22 miles across the Delaware Bay from the lighthouse to the small town of Bowers, Delaware.
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“In the Delaware Bay, the fetch is limited,” Farrell said. “And so there’s a very finite wave size that you will see, no matter what kind of storm you have. That means the fabric material to be put in place will likely work fine. You’re not going to see 15-foot breakers.”
Engineers have to determine the best way to protect the coastlines — and that means using different barriers to get the job done. Here are a few approaches that you may have seen used in New Jersey.
Geotubes
Geotube, a brand name for a kind of long sandbag, was trademarked by the Netherlands in 1994. Farrell uses the more generic name of geotextiles. Sand and water are pumped into a large synthetic fabric sleeve. The water drains off, leaving the sand contained.
“The sand doesn’t move away so readily. But it’s not such a hard structure that it can’t be removed. You can cut the thing open and pull the fabric away,” leaving the sand in place, Farrell said. They can range from 3 feet wide by 12 feet long to hundreds of feet long and 10 to 12 feet wide.
“The biggest one I’ve seen put in place in New Jersey was in Sea Isle City,” he said. That one was about 2,400 feet long.
Sunlight is a weakness for this style of shore protection, he said. Manufacturers continue to improve the product, but UV rays can break down the fabric over time. Often, Geotubes are covered in sand, both as protection and to make them look more like dunes.
That’s the DEP’s plan at the East Point Lighthouse, and what was done along Ocean Drive in northern Sea Isle City and southern Strathmere. A portion of the Geotube was exposed there after Hurricane Sandy but was reburied as part of a beach replenishment since then.
Sand replenishment
Cape May lighthouse in Cape May, New Jersey. (Dale Gerhard, The Press of Atlantic City/AP Photo)
When sand disappears from beaches, the obvious solution is to put it back. The process has been going on for decades, even before the Army Corps of Engineers began a 50-year commitment to protect Cape May’s beaches in 1991.
That set the standard for future projects. From Seaside Heights to Avalon, and for most of New Jersey’s beach towns, a huge dredge pumping sand from offshore to rebuild eroded beaches has become a routine sight.
Even before Hurricane Sandy brought a flurry of federal spending to beaches, the cost of beach replenishment in New Jersey had topped $1 billion, with no end in sight.
Farrell said there is little choice in the matter.
“If you want to have a recreational facility, you’re kind of limited to beach fills,” he said. “In other words, you bring in material and replace it as it moves elsewhere, or bring it back from where it moves to.”
The replenished beach will protect properties from future storms and keep the summer visitors happy.
Farrell said the sand moves in predictable ways.
“After a beach fill, that sand doesn’t melt,” he said. “It goes somewhere else.”
Aside from pumping sand in from the inlets offshore, he said, towns could also gather the sand that washed to other areas and return it to the eroded section. He said the next step is to get approvals from regulators. But he predicts resistance.
“It will require some convincing of the folks in that area. They say, ‘You’re not taking my sand.’ Well, first of all, it’s not your sand,” he said.
For instance, North Wildwood’s beaches are extensively eroded, while the beaches in Wildwood and Wildwood Crest to the south on the same barrier island have grown over 20 years, he said.
“It’s real cheap compared to pumping material from offshore,” he said.
The Army Corps of Engineers has made dunes a key component of beach projects. The dunes can block storm-driven waves and serve as a reserve of sand as the ocean removes beach. There has been controversy there, too, with Margate opposing the construction of dunes as part of a 2017 beach project.
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