After heavy rains from remnants of Tropical Storm Lee washed away bridges and roads, overwhelmed sewage systems and may have contributed to at least one Baltimore-area death, the runoff threatened to overwhelm Maryland towns along the Susquehanna River with the biggest flood in almost 40 years.

On Friday morning, Cecil County officials said all but 12 downtown Port Deposit residents had obeyed the evacuation order and left town. Only a dozen went to the town's shelter at Perryville High School, and county spokesman Mike Dixon said it would be closed over low attendance.

The night before, evacuating residents were walking through the murky waters — at times knee-deep — on Main Street and along the train tracks, carrying whatever baggage they could handle. Businesses on the west side of Main Street were already being lapped by the rushing Susquehanna.

The river was forecast to crest at Conowingo dam at 8 p.m. Friday — 10 hours earlier than earlier predictions — and had also been revised downward by about three feet, to 32.3. The record 36.83 feet was set in the aftermath of Tropical Storm Agnes in June 1972.

Exelon Energy Corp., the hydroelectric dam's owner, opened 40 floodgates late Thursday and had warned that all 50 of the main floodgates would be open by 11 a.m. Friday, triggering evacuations in the riverside towns of Port Deposit and Havre de Grace.

On Friday, Dixon said only 48 gates would be open. As of 3:30 a.m., 43 floodgates were open.

"Things are looking a little bit better, but we're still looking at some serious flooding" in Port Deposit, Dixon said.

Port Deposit Mayor Wayne L. Tome Sr. had urged residents to pack emergency kits and leave, noting that all electric, water and wastewater services would be interrupted for the duration of the flooding. A mandatory evacuation took effect at 8 p.m. Thursday.

"This is the most significant [flood] since I've been alive," Tome said.

This week's rains, which are expected to continue Friday, triggered damage across the Baltimore region. At Patapsco Valley State Park, visitors had to be evacuated after the river suddenly surged over its banks. Several bridges in Baltimore County, including one over Norris Run near Reisterstown, were severely damaged. And significant sewage spills were reported in several localities.

But the most serious problems arose in waterside communities such as Port Deposit and Havre de Grace.

Port Deposit's residents (821 in the last census) were "not too happy" about the evacuation, Tome said, adding, "They're pretty calm; nobody's going crazy. Most of the older folks are used to it. They respect and know the river, and they … instill some calm in fellow residents that haven't been here that long."

Jeremy and Cristina Justice shouldered heavy backpacks as they awaited their ride out of Port Deposit. A foot of water was flowing through the first floor of their North Main Street home by Thursday evening.

"The water has been cascading in," said Jeremy. "It's probably going to reach the second floor."

"We're going to be cleaning up a lot of mud and silt when we get back," said Jeremy, a 25-year resident of the town who has evacuated several times in the past. The Justices are independent contractors and expect to handle many repairs on their neighbors' home as well, once floodwaters recede.

Some 400 residents of low-lying sections of Havre de Grace were also ordered out Thursday as the water began spilling into the lower levels of riverfront homes.

"The Havre de Grace Police Department is going door to door, to make sure everyone who needs to get out has gotten out," said Harford County spokesman Ben Lloyd.

The town's most critical concern Thursday night was the county-owned Citizens' Care & Rehabilitation Center, where about 165 residents, most of them frail or handicapped and elderly, had to be moved out, according to Harford County Executive David Craig.

At 8 p.m., more than 30 ambulances, five Harford County Transit buses and one medical aid bus from Howard County were lined up to move residents to similar facilities in Harford and Baltimore counties.