Floodwaters from the rain-swollen Susquehanna River have flushed 30-foot trees, gnarled clumps of branches, road barricades and old tires into the upper Chesapeake Bay--a flotilla of debris that is alarming boaters and environmental activists.
The U.S. Coast Guard is broadcasting warnings three times a day, cautioning boaters to be on the lookout in the northern end of the bay. Most of the debris, which could damage boats and smash into piers and docks, was unleashed by the heavy rains accompanying the remnants of Hurricane Ivan. The extra water forced the weekend opening of the Susquehanna dams.
"There's all this stuff in the water," said Mark Huppert, a fisherman who had to navigate his way Tuesday night around tree limbs and floating barrels near Pooles Island. "You definitely could do some serious damage to your boat if you didn't watch out."
Rising waters over the weekend overwhelmed Pennsylvania and New York rivers that empty into the Susquehanna, threatening Port Deposit and prompting operators of the Conowingo Dam to open 33 of its 50 floodgates Sunday night. By yesterday, the river had receded below flood level and only nine gates were still open.
But marine authorities cautioned that the uprooted trees and piles of debris that raced through the floodgates will likely linger in the Chesapeake Bay for weeks.
Environmentalists fear another long-term consequence: large amounts of sediment could have been carried into the bay along with the debris.
The flooding occurred just as environmental groups were celebrating a rebound in underwater grasses. The grasses, crucial for crabs and waterfowl, have been in decline for years.
Last month, however, scientists found close to a dozen species of tall, thick grasses in the upper end of the bay.
Sediment "clouds the water, which will impact the growth of the grasses," said Scott Phillips, the U.S. Geological Survey's Chesapeake Bay coordinator. "It can actually bury some of the grasses if the sediment load is large enough."
The water as far south as a mile from the Bay Bridge by yesterday had turned a deep brown -- the color of dark coffee, according to Karl Willey, a captain who runs an oyster-replenishing program with the Chesapeake Bay Foundation.
"It's amazing. I've never seen it like this before," said Willey, who was interviewed by phone from his boat. He said he could see a swirl that looked deeper and darker than the water did after Tropical Storm Isabel.
Environmentalists believe there has not been this much sediment or debris since 1996, when melting snow overwhelmed the Susquehanna dams and dumped a record amount of rubbish in the bay.
Nonetheless, scientists were cautiously optimistic that it would not significantly harm grass growth, which is winding down for the season.
Phillips said his staff is still analyzing water samples taken earlier this week to assess the environmental consequences of the floodwaters dumped into the bay. State Department of Natural Resources staff will also do their own study in the upper bay.
Boaters face a more immediate risk as debris becomes less visible as it starts to sink below the surface, threatening to smash propellers and hulls and even tip vessels. Coast Guard patrols are working to mark the most hazardous refuse and will keep broadcasting warnings on marine radio until Oct. 4.