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Isabel causes extensive shoreline erosion

Sun Staff

The ecological damage to Sharps Point isn't hard to spot.

Some of the steep, grassy banks at the mouth of Whitehall Creek in Anne Arundel County are simply gone, wiped away by surging waters of the <Chesapeake Bay from Tropical Storm Isabel.

"This is extreme damage, thousands of pounds of dirt sediment that have been carried into the bay," said Rich Batiuk, associate director of science for the U.S. Environmental Protection Agency's Chesapeake Bay Program.

Up and down the bay, scientists and government officials are beginning to catalog Isabel's environmental consequences, including extensive shoreline erosion, large amounts of sediment and nutrients, untreated sewage and spilled oil.

Yesterday, scientists and representatives from the bay program and Chesapeake Bay Foundation toured parts of Whitehall Creek by boat, checking water quality and clarity and taking inventory of some of the land lost along this small tributary just west of the Bay Bridge.

"That bank is 6 to 10 feet farther back than it was last week," said Bart Jaeger of the foundation, pointing to an area of shoreline that he frequently passes while giving educational tours. "It was just gouged out."

The large amounts of erosion stripped sediments off the shore and pumped tons of fine particles into the bay and its tributaries, scientists said.

Dredging up a sample of the bottom off Sharps Point with a metal scoop, Tiffany Granberg of the bay foundation found the usual mud - but covered with a top layer of sediment from the storm.

"It's very soft, very fine," Granberg said as she ran her hands through the mud. "This is the kind of stuff that covers up the grasses and keeps them from growing, when they're such a vital habitat for fish and crabs."

Isabel didn't carry as much sediment into the bay as scientists had feared when it was approaching the mid-Atlantic coast and was classified as a much fiercer storm.

"In terms of climatic events, this wasn't nearly the worst-case scenario," said Bob Wood, a fisheries biologist with the National Oceanic and Atmospheric Administration's Chesapeake Bay office in Annapolis. "The amount of rainfall was much lower than [Tropical Storm] Agnes. We didn't get the scour [of sediment] behind the Conowingo Dam."

Had Isabel produced more rain in areas feeding into the Susquehanna River, scientists say, years of sediment built up behind the Conowingo Dam would have been dislodged and sent into the bay.

Instead, Isabel produced about 3 inches of rain or less in Maryland and more northern states, compared to 8 inches or more during Agnes in 1972.

The average daily river flow into the bay is about 50 billion gallons. The peak during Isabel was 213 billion gallons of water per day, compared to 687 billion during Agnes, according to data released yesterday by Scott Phillips, the U.S. Geological Survey's Chesapeake Bay coordinator,

"We didn't see as much sediments as with Agnes," Phillips said. "But here we have a lot of shoreline erosion, and there wasn't the erosion or the wind in Agnes. This shoreline erosion might be a more immediate impact on the underwater grasses and other parts of the bay."

Water-quality monitors on the Magothy River from the Maryland Department of Natural Resources recorded a more than tripling of turbidity - a lack of water clarity - during last week's storm, an illustration of how much shoreline erosion occurred and how much soil was carried into the tributaries, said Bruce D. Michael, DNR's chief of water and habitat quality.

"We won't be able to tell the full impact until next year, as we see some of the living resources," Michael said. "It won't just be from this storm, but from the whole summer. It's been such a wet year that we have had a lot of runoff of nutrients and sediments."

In the days immediately after the storm, some tributaries have been too cloudy from sediment runoff, but fishing on the main portion of the bay appeared to quickly return to normal for those people who can get boats onto the water through damaged marinas and ramps, said Richie Gaines, a charter captain and president of the Chesapeake Guides Association.

"My biggest concern is the long-term effects," Gaines said. "You've got all this sewage, all these sediments, and we know the bay is already having problems.

"It's like heart disease. You can't really see it. You can't feel it. But you know it's inside, doing its damage," Gaines said.

Scientists said they don't believe there will be long-lasting consequences to the bay from the millions of gallons of untreated sewage - dumped from plants and pumping stations that were flooded or without electricity - or the oil spilled from tanks of flooded homes.

Nevertheless, the bay - suffering from decades of pollution and runoff from agriculture and residential development - isn't as resilient when it comes to bouncing back from strong storms and wet summers, said Theresa Pierno, a bay foundation vice president.

"We think we'll see a major depletion in our underwater grasses," Pierno said. "We expect there to be more nitrogen pollution, more phosphorus, in the bay. We haven't done enough in these areas yet."

In the short term, the Maryland Department of the Environment has banned shellfish harvesting in the bay through at least the weekend - though it expects that prohibition to be lifted by the Oct. 1 opening of the state's oyster season.

As the scientists toured the eroded shorelines along Whitehall Creek, they said the record tidal surge - 7.2 feet above mean low water in Annapolis, tying the high of 1933 - illustrated the importance of buffers such as grasses and trees.

In one home's back yard, dirt was ripped away to the edge of a swing set, while a nearby area with grasses and trees at the water's edge appeared to suffer little shoreline damage.

"You can see that where there are trees, the roots were digging down and holding in soil, so not as much was lost," Batiuk said. "There's a clear example of what the bay will do, and what the bay will do if you leave in natural buffers."

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