Some 4.7 million cubic yards of Chesapeake Bay shoreline is eroding each year, adding sediments, toxics, and nutrients to the water.
In the past century, 45,000 acres of shoreline has eroded — an area equivalent to the District of Columbia.
Those figures are presented in a new U.S. Army Corps of Engineers report, "Chesapeake Bay Shoreline Erosion Study," which was done in cooperation with the states of Maryland and Virginia.
The $3.5 million study found that the average rate of erosion along the 7,300 miles of shore that line the Bay and its tidal tributaries was a foot a year. In some places, however, the shore is receding at a rate of 10 feet a year.
"This erosion results in a significant loss of valuable shorefront land and wetland habitat, damage to buildings and other structures, diminished beach capacity at recreational areas, and damage to valuable cultural and historic resources," the report said.
The report identified 135 miles of shoreline, located in 91 areas or 'reaches,' as subject to 'critical' erosion — erosion that is both rapid and poses a threat to property or resources.
However, little of the critical area that is in private ownership will receive shoreline protection from a federal project because the law requires that public access must be provided at shorelines protected by the federal project — a requirement to which few landowners will agree.
"In very few cases around the Chesapeake Bay where federal projects were found feasible did we find private landowners or community associations willing to provide public access in exchange for the project," said Noel Beegle, chief of the Basin Planning Branch in the Corps' Baltimore District.
MORE sediments enter the Bay from shoreline erosion than from the rivers that feed the Bay, according to the report.
About 4.7 million cubic yards are eroded from the shores each year compared with the 4.3 million cubic yards washed in from rivers. Also, the report said, portions of the shoreline under the level of the water are eroded and redistributed in the Bay, further adding to the sediment load. If this "below water" portion is figured in, the total shoreline loss equals 11 million cubic yards per year.
The shoreline losses add nutrients to the Bay. A recent study by the Virginia Department of Conservation and Recreation estimated that shoreline erosion contributes 1.37 million pounds of nitrogen and 0.94 million pounds of phosphorus a year to Virginia waters. That's equivalent to 5.2 percent of the nitrogen nonpoint source load and 23.6 percent of the phosphorus nonpoint source load entering the Bay from Virginia, according to the Corps' report.
Losses are not equally distributed. The study found that the Eastern Shore of both Maryland and Virginia suffered a faster rate of loss than the Western Shore. A few islands in the Bay, notably Sharps Island which once measured more than 600 acres, have disappeared completely.
Some scientists believe that sea level rise associated with global warming could accelerate erosion rates, but the report did not assess such potential impacts citing a lack of data. But, it cautioned, "an increase in sea level rise could cause the erosive power of waves to be translated further inland."
Also, because some of the data used in determining shoreline erosion rates is years old, no analysis was made as to whether the rate of erosion is increasing as some scientists believe is happening.
Erosion caused by wind and waves has shaped and reshaped the Bay since it was formed out of the Susquehanna River some 10,000 years ago. Almost all erosion is caused naturally, though some human related activities can cause problems in certain areas. For example, shipping and boating can generate waves, and the loss of submerged aquatic grasses due to pollution removes a natural buffer to erosion.
But erosion also carries economic and environmental impacts.
Eroded sediments fill channels forcing them to be dredged to maintain shipping lines to ports. As land is eroded, it takes away people's property — and sometimes even their homes. It also takes away from the local tax base. Increased sediments may cause a reduction in the fishery, while erosion can destroy parks and access areas, archaeological sites, and other resource areas.
Erosion may be a natural activity, but it can further stress living resources already beset with other problems.
Adverse environmental impacts include smothering the of habitats of oysters and other bottom dwelling organisms. Also, when the disturbed soils become suspended in the water they reduce the light available for the submerged aquatic vegetation needed for the survival of other fish and waterfowl species. Nutrients, and in some areas toxics, are brought into the water as the soil erodes.
"There can be more impact from shoreline erosion than you ever thought about," said Leonard M. Larese-Casanova, director of Maryland's Shore Erosion Control Program.
Shoreline protection can cost hundreds of dollars a foot, so the cost of protecting a mile of shoreline can easily approach or surpass $1 million.
Although controlling coastal erosion may produce some benefits for the Bay, the idea of using public money to protect individual beach fronts while others are denied access is not attractive to many people.
"You don't have a lot of support for helping someone protect their own property when they're the ones getting all the benefits," said Lee Hill, chief shoreline engineer with the Virginia Shoreline Erosion Advisory Service.
Both Maryland and Virginia have programs that give property owners technical advice on how to handle shoreline erosion problems. Maryland even offers financial aid in some instances. And the federal government is involved only when there is a willingness to provide public access or there is a substantial economic impact.
So most of the job of protecting Bay shorelines — about 99 percent of which is privately owned — falls on individuals. In Maryland, for example, while the state programs protected between three and four miles of shoreline last year, private owners sought permits to do about 32 miles of work without state aid.
Even when state officials give advice, it may not have to be followed. "It's up to them," said Virginia's Hill."³We're not regulatory in nature. They can take our advice or leave it."
To combat shore losses, the Corps report said, owners have resorted to building individual bulkheads, riprap revetments, and other measures along the shore that "could eventually result in the entire Bay shoreline being armored, without concern for the environmental impacts of these types of structural measures and consideration of other less damaging alternatives," the report said.
A better way to approach the issue, the report suggests, is to develop a comprehensive Baywide shoreline erosion control plan that would coordinate efforts of the Corps and state and local governments.
Beegle said a comprehensive plan might identify specific areas of shore and recommend what types of erosion control techniques are best suited for that area. The recommendations could then be incorporated into local plans.
"Right now," Beegle said, "erosion control is kind of in the hands of the individual property owners."
In some areas, though, constructing certain types of erosion control devices may actually cause increased erosion someplace else. Likewise, if one landowner builds, say, a bulkhead, and his neighbor builds nothing at all, the land on the second owners property may erode away and allow the water to 'flank' the first owner's bulkhead.
"I can show you many pictures of bulkheads that are 30 to 40 feet out in the water," Beegle said.
Virginia¹s Hill agreed that a comprehensive plan could be beneficial, but cautioned that it would be difficult to implement. Such a plan, for example, may recommend doing nothing along one stretch of beach because material from that beach was building up a more critical area. Likewise, if a plan suggested structural improvements along another whole stretch of beach, it could entail huge costs for property owners if they were to foot the bill.
"It's a nice idea, but actually implementing it could be a bear," Hill said. "People have different opinions about property owner rights."
Whether such a plan is developed or not, the report did suggest some other ways that could help erosion control efforts.
For example, it suggests that informational booklets be prepared showing the effectiveness of various erosion control techniques that were tested in the Chesapeake as part of the study, some of which had relatively low costs. Some techniques not only protect the shoreline but can provide environmental benefits.
More modeling is also needed, according to the report. Beegle said little is known about where eroded sediments end up in the Bay. If it could be determined where sediments that fill shipping lanes were coming from, for example, an effort could be made to stem erosion in those areas and thereby reduce dredging costs as well as environmental impacts.
The report also suggested that some dredge material be used to build small islands and wetlands to replace fish, shellfish and wildlife habitat that has been lost to erosion.
"Certainly it is a difficult problem to tackle and control, but you can't just throw up your hands and say you can't do anything about this," Beegle said.
Copies of the report are available for $5, and copies of the technical appendices are $10 each. For a copy of either, write to Claire D. O¹Neill, Study Manager, U.S. Army Corps of Engineers Baltimore District, P.O. Box 1715, Baltimore, MD 21203-1715. Checks should be made payable to ³Finance and Accounting Officer, U.S. Army Engineer District, Baltimore.²
Common techniques to hold the ground on shoreline erosion
Many techniques are available to help control shoreline erosion. Their effectiveness varies depending on the characteristics of a particular site, such as the power of the waves and the types of soil.
Some, such as bulkheads or revetments, provide protection for slopes immediately behind them making them a common choice for the protection of bluffs, but may have consequences such as blocking the deposition of sediments elsewhere along the shore, thereby speeding erosion someplace else.
Likewise, vegetation may help provide extra protection for an area such as a wetland, but would not do the job of protecting a bluff.
Costs, too, vary. Vegetation planting is relatively inexpensive, but construction of some structures may reach hundreds of dollars a foot. As part of its study, the Corps experimented with the construction of low-crested breakwaters — low piles of rock built off shore at various intervals — and found they were effective at breaking up wave energy and protecting larger areas of beach, often at less cost than other structures.
Here¹s a look at common erosion control techniques:
Bulkhead: A structure or partition to retain or prevent sliding of the land. A secondary purpose is to protect the upland against damage from wave action.
Breakwater: A structure protecting a shore area, harbor, anchorage, or basin from waves.
Groin: A shore protection structure built (usually perpendicular to the shoreline) to trap sand and other drift material or retard erosion of the shore.
Perched beach: A beach or fillet of sand retained above the otherwise normal profile level by a submerged dike, thereby protecting it from wave action.
Vegetation: Planting of vegetation can help stabilize slopes and prevent erosion, though vegetation alone cannot prevent erosion caused by heavy wave action.
Slope stabilization: Steep slopes can be regraded, planted and given improved drainage to make them less susceptible to erosion.
Beachfills: A practice of placing large quantities of sand on the shore, taken from dredging, piped in from offshore deposits or hauled in from trucks.
Low-crested and headland breakwaters: A breakwater that essentially consists of low-crested piles of stone offshore which break up wave energy, creating an area in the lee of the structure which promotes sediment deposition and development of a stable beach.
Where to get help for shoreline erosion
Both Maryland and Virginia offer programs to help property owners with shoreline erosion problems.
In Maryland, the Shore Erosion Control Program offers technical assistance to property owners, communities, and counties experiencing shore erosion problems. The program has between $2 million and $3 million available annually in a revolving fund to make interest-free loans for structural improvements along shorelines. Recipients are chosen based on the severity of the problem. Also, $500,000 is available on a matching-fund basis for non-structural improvements, such as vegetation planting. For more information, contact the program office at (301) 974-7853.
In Virginia, the Shoreline Erosion Advisory Service offers on-site inspections of shorelines, followed by advice on environmentally sound corrective measures that can be taken. Also, the office will inspect property that people are seeking to buy to determine the potential for erosion problems. The office will also review plans for structural devices. No loans or grants are available for private property. Grants are available, on a 50-50 cost share basis, for conservation projects at public beaches through the Board on Conservation and Development of Public Beaches. For more information on the SEAS program, call (804) 642-7121.