Shortly before noon Saturday, Exelon Power Co. had opened 26 of the floodgates on Conowingo Dam to accommodate the rush of rainwater and melting snow flowing down the Susquehanna River on the way to the Chesapeake Bay.
The more gates on the hydroelectric dam that are opened, the greater the risk of flooding, particularly in the town of Port Deposit, a few miles downriver.
With more than half the gates open, the town heard a warning siren and braced for what residents call "a high-water event."
But by 2:30 p.m., the river had crested and the power company had closed two gates.
"It looks like the river has reached its crest," said Port Deposit Mayor Kerry Abrams. "We still have water in our basements, our backyards and in the town park. It won't go down until they are at 18 gates. But it looks like we have made it through. With clear skies and no pending rain, we are extremely lucky this time."
The Susquehanna, which rises from a spring near Cooperstown, N.Y., and takes water from 30,000 miles of feeder streams, flows nearly 500 miles through three states before emptying into the Chesapeake Bay.
The river basin is one of the nation's most flood-prone areas, and its "main stem is more prone to ice jams and subsequent flooding than any other river east of the Rocky Mountains," the Susquehanna River Commission reports.
The worst flooding in recent memory occurred after Tropical Storm Agnes, which dumped more than 7 inches of rain as it made its way along the Eastern seaboard in June 1972. At the June 24 peak of the flood, which saw the river crest at 40.91 feet, all 50 of Conowingo Dam's gates were opened. Much of the town was inundated.
Longtime residents know to base their reactions on the number of gates opened.
"When they get back down to 18, the water will recede and we can start to clean up," Abrams said.
That will likely be Monday, she said.
"It's not only the water," she said. "It's all the debris left behind once it recedes."