Plume of muck from recent storms heading our way

The satellite photo paints an ominous portrait: a solid wall of brown muck headed south toward Virginia down the Chesapeake Bay.

NASA satellites are tracking and photographing from space what scientists are calling a giant "sediment plume" resulting from massive flooding on the Susquehanna River in Pennsylvania during Hurricane Irene and, more recently, Tropical Storm Lee.

Scientists estimate that the plume, loaded with muddy runoff from farms and overwhelmed storm drains, tree limbs, fertilizers, wastes and even water heaters and a few outhouses, will push through Hampton Roads in the days ahead before exiting the Bay into the Atlantic Ocean.

Satellite images from this week show a chocolate-milk-like sheen slowly moving from the top of the Bay, where the Susquehanna River empties, to the Maryland-Virginia line. On Wednesday, images showed the plume inching its way into the mouth of the Potomac River in Virginia.

"Basically, the upper half of the Bay is entirely brown," said Bob Orth, an aquatic plants specialist at the Virginia Institute of Marine Science who studies underwater grasses in the Chesapeake. "It's absolutely extraordinary."

Scientists who have witnessed the plume in boats describe it as patchy, with some chunks a half-mile long, and reaching depths to the bottom of the Bay.

"Some of my colleagues who have seen flooding impacts on the Hudson River and the Mississippi River say they have never seen anything so dense, so large, as this," said Michael Ford, ecosystem science manager for the National Oceanic and Atmospheric Administration's Chesapeake Bay Office, based in Maryland.

"This is certainly new for our generation," Ford added.

The National Weather Service is comparing the floodwaters to those from Hurricane Agnes in 1972, a storm that devastated aquatic life in the Bay.

But that hurricane struck in June, when baby fish were just learning to swim and underwater grasses were still blooming. Irene and Lee walloped the Bay much later, in late August and early September, when most of these natural cycles were winding down.

So the timing of Irene and Lee is much better ecologically for the Bay than Agnes, scientists say, and the storms will not likely leave such a nasty, lasting mark.

The Chesapeake Bay Program, overseen by the U.S. Environmental Protection Agency, estimates the impacts to living organisms will be minimal but still cautions that the sediment plume could cover fragile oyster reefs and grass beds under a blanket of mud.

In Virginia and elsewhere, scientists and other experts will wait until the dust settles - silt, actually - before analyzing the consequences.

Rick Hoffman, who tracks water quality trends in the Bay for the Virginia Department of Environmental Quality, said researchers are scheduled to go out with monitoring equipment next week. Teams from Old Dominion University and the Virginia Institute of Marine Science will assist, he added.

It could take weeks, if not months, to fully comprehend the effects, scientists said.

In some ways, though, Irene has helped the Bay. It churned stagnant waters and broke up harmful algae blooms, including those in the James and Elizabeth rivers in Hampton Roads, which had resulted from summer heat and excessive nitrogen and phosphorus from sources such as stormwater from city streets, new development sites, farms, parking lots and animal wastes.

Overall, Irene saturated the ground in wet places such as northern Maryland and Pennsylvania. While it barely touched coastal Virginia, Lee followed with torrents in the upper Bay that had little place to go, especially in the already-flooded Susquehanna River basin, which is the largest freshwater source in the Bay.

Gatekeepers at the huge Conowingo Dam on the southern Susquehanna had to open the flood gates, allowing a crush of dirty, muddy stormwater to rush freely into the Bay.

The plume began to form last week, scientists said, and has been rolling southward ever since, making boating hazardous in some places in the northern end of the Bay.

Ford said he does not expect the plume to be as intense by time the it reaches Hampton Roads. Still, he said, local residents should notice a change in the color of the Bay, from dark green to chocolate brown.

Environmental groups said the plume illustrates why more needs to be done to contain sediment on land and reduce nutrients that spark algae blooms and steal oxygen from reaching the Bay.

States from Virginia to Pennsylvania are working on new and more aggressive pollution-control plans, as pushed by the Barack Obama administration, though those efforts are being challenged in courts by farm and development groups.

"As many have observed, the Bay's health shouldn't be hostage to the weather," the Chesapeake Bay Foundation said in a statement. "A healthier, more sustainable Bay and Bay watershed would be better able to 'weather' such storm events."

Scott Harper, (757) 446-2340, scott.harper@pilotonline.com