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The most obvious sign of beach erosion is occurring along the coast of Cape Henlopen State Park. When the World War II observation towers were built in the 1940s, they were about 200 feet from the shoreline. Today, they are threatened by waves at high tide and during storms forcing the Fort Miles Historical Society to take steps toward beach replenishment in the area.
Tony Pratt, Department of Natural Resources and Environmental Control (DNREC) shoreline program administator, said he looks at the two towers another way. “I had a discussion with some people on the beach about the towers. They were talking about how bad the beach had eroded,” he said. “I asked them if it was really erosion. There was still a great dune system in place and plenty of room for recreation. The beach was still there.”
Even so, the towers, now surrounded by water at high tide, are symbols of a problem that has far-reaching economic implications to the state. Eroded beaches equate to a loss of tourism dollars.
Delaware has 24.5 miles of beaches, with 12 miles in state parks, visited by 6 million people each year. Those visitors generate an estimated $850 million in tourism dollars.
So erosion control has become a top priority for the Department of Natural Resources and Environmental Control, the agency charged with beach management.
Preserving the tourism industry is why millions are spent on beach replenishment projects to protect the valuable shoreline.
Erosion and beach management
For eons the ebb and flow of the tides, the wind and waves have sculpted the coast. In more recent times, the ravages of erosion have made news; consider the fate of the Cape Henlopen Lighthouse. In 1765, the lighthouse was 1,600 feet, a quarter-mile, from the shoreline. In 1926, the lighthouse made national news when it fell into the sea, a victim of severe coastal erosion. Today, the ocean covers the lighthouse base. In that 161-year time span, the sea claimed an average of 10 feet of land per year along the Cape shore.
A DNREC report lists an anomaly that occurred in the late 1970s. From 1976 to 1979, a DNREC survey revealed that 60 feet of beach had vanished from Fenwick, and a similar amount was gone from Dewey and Rehoboth as well.
Even so, Pratt points out that trying to chart erosion is like predicting the weather.
“It would be a disservice to release an average annual condition or an average erosion rate,” he said. “I’m convinced the beaches go through cycles of quick erosion and through decades of stability.”
“Erosion is as natural as aging and dying,” Pratt said.
And for most of history, beach erosion was not a problem. The Native Americans never built permanent structures along the shoreline, and the first settlers on these shores quickly moved inland to get away from the instability of the beach, said Pratt.
It wasn’t until the early part of the 20th century that state officials started paying attention to beach management as people started to put down roots along the shore.
A system of groins, not be confused with jetties, were built in beach communities from Ocean City to Lewes.
“They were built to slow down the movement of sand and build up the sand by the groins,” Pratt said. “Groin fields were everywhere.”
The problem with groins is that they allow sand to build up on one side, but to diminish on the other side.
Dune grass, groins and beach fencing were the tools of beach management from the 1930s to the 1960s.
Pratt said in the 1970s and 1980s a new beach management practice came into vogue – beach replenishment, or nourishment. In 1972, the Beach Preservation Act established a comprehensive beach and dune management program administered by DNREC.
Then in 1986, Gov. Mike Castle helped establish the Environmental Legacy Program to “assure the continued existence of beaches in Delaware that will provide for anticipated recreational needs and a cost-effective level of storm protection for coastal properties, structures, and infrastructure for the next 25-plus years.”
“There became a huge demand for the beaches and there was much more of an economic impact than ever before,” Pratt said.
The boom had started.
Beach nourishment
“Nourishment is a much better solution because you are replacing what you lost. It’s really like any kind of maintenance. You can’t do it and walk away,” he said.
Pratt said nourishment does not really prevent erosion or stop the movement of sand. “We are resetting the erosional clock by adding sediment to the system and re-establishing the buffer of sand between the ocean and structures,” said Pratt.
A 1995 National Research Council study on beach nourishment reported that it is a viable engineering alternative for shore protection and is the principal technique for restoration.
According to the award-winning DNREC publication, “Striking a Balance – A Guide to Coastal Dynamics and Beach Management in Delaware,” the primary benefits of beach nourishment include storm damage reduction and enhanced recreational and tourism opportunities.
DNREC officials wrote in the report that a wider beach not only acts as a buffer to absorb wave energy, but it also provides a reservoir of sand that could be transported to an offshore bar, reducing the amount of wave attack on the upper beach, thereby reducing the amount of erosion. The report concluded that coastal engineers said even small additional widths in beaches have big impacts in storm events, and the wider the beach, the more people can enjoy it.
Once beach replenishment starts, the process is ongoing. The 2005 $18 million replenishment at Dewey and Rehoboth was not just a one-shot deal, but part of a 50-year commitment by the Army Corps of Engineers to maintaining the sand along the coastline. That commitment depends on funding.
Funding from the federal government has become an issue as officials scramble to get the Bethany-Fenwick replenishment project off the ground this winter.
What about the sand?
The sand along the Delaware shore mostly comes from adjacent beaches and not as sediment runoff from rivers.
So theoretically, Pratt said, over many years, beaches would disappear. “We don’t truly understand where the sand comes from. We understand how it moves and where it goes, but not where it comes from,” he said.
Pratt said the most plausible theory is that there are extensions of old land necks out in the ocean feeding sediment back into the system. “We have never had any research to prove this theory about the eroding land necks,” he said.
Sand is constantly in motion, going in and out with the waves. Pratt said a wave rolls up on a Delaware beach an average of every 10 seconds. That equates to 8,640 waves a day and 3.1 million waves a year.
“Think how many waves that would be in your lifetime, and every wave moves sand either north or south.”
Pratt said the balance point along the Delaware coast is Fenwick where just as much sand moves north as moves south. “The closer to Cape Henlopen, the less influence the northern waves have and the more influence the southern waves have,” he said.
In Dewey and Rehoboth, in what Pratt calls a conveyor belt, the sand migrates north until it reaches the tip of Cape Henlopen. The cape is in a constant state of growth. DNREC officials estimate the cape has advanced 6,000 feet out into the Delaware Bay over the past 200 years.
Pratt said as much as 225,000 cubic yards of sand moves to Cape Henlopen each year from Rehoboth and Dewey, while about 100,000 cubic yards moves toward the Indian River Inlet from Bethany and parts of Fenwick.
The sand also moves with the seasons. In the summer, the waves are small and rolling and the beach is wide, and in the winter the waves are large and sharp and the beach is broken down and narrow. It’s the natural process that has been occurring along the coast for centuries.
Pratt said the seasonal change can be 100 feet or greater from summer to winter as the sand moves onshore and offshore.
Pratt said there is always the option to do nothing and let nature takes its course.
“We could walk away and let all the tourists go to Maryland because they are committed to an ongoing nourishment program,” he said. “But that is not the imperative. That is not what the legislators want, and not what the people want. It’s a good investment to buy sand.”
Next week: The economics of beach management.
Understanding Beach Terms
Coastal erosion: Erosion occurs when there is a net loss of sand from the beach system. The loss could be temporary or permanent.
Groin: A shore-protection structure that juts into a body of water perpendicular to the shoreline built to restore an eroding beach by intercepting long shore drift and trapping sand.
Jetty: A structure designed to protect a harbor by directing or confining the stream or tidal flow to a selected channel, or to prevent beach erosion.
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