The downpours of rain brought by Tropical Storm Lee in recent days will likely contribute to worse than normal water quality in the Chesapeake Bay this year, despite accelerated efforts to clean up the estuary, according to Maryland’s top water quality analyst.
Huge gouts of rain are causing near-record flooding along the Susquehanna River, the National Weather Service reports. All this water is flushing sediment and fertilizer from Pennsylvania down into the Bay’s largest tributary, said Bruce Michael, Director of the Resource Assessment Service at the Maryland Department of Natural Resources.
“Rains from the remnants of Tropic Storm Lee impacted the Susquehanna River basin far more than Hurricane Irene and will deliver major nutrients and sediments to the Bay,” Michael wrote in an email. “Overall, Bay water quality in 2011 will probably be worse than average in spite of accelerated restoration efforts by Maryland and our Bay watershed partners.”
At top and below are photos of flooding in Harrisburg, Pa., where the mayor ordered the evacuation of about 10,000 residents and threatened to arrest curious onlookers who ventured too close to the swollen waterway.
Near the southern end of the Susquehanna, the floodgates in the Conowingo Dam in northeastern Maryland have been opened to cope with more than 600,000 cubic feet of water per second. So much water is gushing through the dam that the flow is digging up and releasing downstream “a significant amount” of sediments and nutrient pollution that had been trapped behind the dam, Michael said.
The Maryland Department of Natural Resources is warning boaters on the Susquehanna to be “extra vigilant and keep a lookout for floating debris that could be hazardous to navigation.”
At 12:45 p.m. today (September 8), water levels in the Susquehanna River had reached 35.42 feet at Wilkes Barre, more than 13 feet above flood stage, according to the National Weather Service.
The agency is projecting that the river will rise at least another 2.6 feet, cresting at 38 feet. This will make it the worst flooding in almost four decades, since Hurricane Agnes in 1972, said Charles Ross, a hydrologist with the National Weather Service in State College, Pennsylvania.
Farther south in Harrisburg, the river had reached 24 feet by 5 p.m. today, a flood higher than level the weather service classifies as “major flood stage,” or 23 feet.
Mandatory evacuations were ordered in several low lying areas along the Susquehanna River in Pennsylvania, including Luzerne County, West Pittston, Exeter, Jenkins Township, Plains Township, Hanover Township - Dundee section, Plymouth, Plymouth Township, Hunlock Township, Nescopeck, Mocanaqua and Shickshinny, according to the (Wilkes-Barre) Times Leader.
In Maryland, the mayor of the town of Port Deposit beside the Susquehanna River also declared a mandatory evacuation, The Baltimore Sun is reporting.
More rain is in the forecast today through Friday with the possibility of one to three inches. Since Jan. 1, more than 44 inches of rain has fallen, nearly 19 inches above normal.
“A travel ban is in effect in Wyoming County (Pennsylvania) due to the flooding of the Susquehanna River,” the Times-Leader is reporting. “Tunkhannock Township has declared a state of emergency. Only essential travel and emergency personnel are permitted on the roadways.”
That storm happened in June, and it devastated underwater grasses downstream in the Chesapeake Bay, killing thousands of acres of this critical aquatic vegetation.
The current rainfall is unlikely to have much of an impact on Bay grasses, because it is later in the season and the grasses are already dying back as part of their natural lifecycle, said Bob Orth, an expert on aquatic vegetation at the Virginia Institute of Marine Science. Hurricane Agnes, by contrast, hit in the spring, when the grasses were sprouting and growing.
"This is going to be an interesting test to see how well these plants persist with these incredible flows," Orth said. "My gut instinct is that (the recent rains) will not have a big impact" on the Bay grasses, he said.
However, the nitrogen and phosphorus pollution carried by the rainwater into the Bay is likely to cause low-oxygen “dead zones” over the next several weeks, said Michael of the Maryland Department of Natural Resources.
For more information on pollution from stormwater, read the Chesapeake Bay Foundation website.
At left is a NASA satellite photo of the Susquehanna River taken on August 31, 2011, as the river flows into the northern Chesapeake Bay. The picture was taken just after Hurricane Irene, and shows chocolate-colored water (evidence of sediment) flowing downstream. More recent quality photos of the river during Tropical Storm Lee are not yet available, because the cloud cover has obscured the satellite view.
By Tom Pelton
Chesapeake Bay Foundation
(Photos of flooding at top and center by Foster Nost of the Chesapeake Bay Foundation)