Amesbury, Mass. ? Authorities warily monitored swift, high rivers and strained dams on Wednesday as New England began to clean up from days of record-breaking rain that dumped up to 17 inches in some places.

Residents and businesses were evacuated in downtown Amesbury, near the New Hampshire border, where the swollen Powow River threatened to push down a stone retaining wall adjacent to a dam and unleash a torrent of water.

“If this blows through, the water’s going to go right through downtown,” said Mayor Thatcher Kezer.

Crews used heavy machinery to pluck debris from the water and cut down trees that could fall into the river.

Meanwhile, work continued in Haverhill to repair a damaged sewer line that was spewing tens of millions of gallons into the Merrimack River. In New Hampshire, officials worked to resolve problems at a series of dams along the Newfound River in Bristol. Loose bolts at one dam had prompted the evacuation of up to 400 families and businesses.

The region’s shellfish industry also prepared to absorb another blow as beds were closed from southern Maine to Cape Cod. Runoff from roads, flooded rivers and overburdened sewage systems pollutes the beds.

More than a foot of rain fell across a wide swath of New England between Friday and Tuesday, creating the region’s worst flooding in 70 years. At least 2,500 people were forced from their homes by the flooding and hundreds of roads were washed out.

Massachusetts Gov. Mitt Romney said Wednesday he was seeking major disaster relief to speed help to those affected.

Police reported a single fatality, a 59-year-old New Hampshire man whose body was found in a partially submerged car north of Boston.