GRANT, Minn. -- It’s easy to miss a flood in disguise.

But the slow-motion rising of water, scattered in dozens of ponds and lakes, has become so destructive that Washington County has declared an emergency.

After one of the wettest years ever recorded, rising waters have damaged dozens of homes. Officials estimate that $5 million is needed to buy flood-prone houses — and that’s only in one of the county’s eight watershed districts.

Roadways have been submerged by the stealth flood. One of them is busy county Highway 12 in Grant, a problem that would cost $500,000 to fix by raising the road by four feet.

“We are really in unprecedented times,” said Wayne Sandberg, the county’s Deputy Director of Public Works.

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He said that when people think of floods, they usually think of raging rivers breaking out of their banks.

This flood is different, he said. Heavy rainfall on the flat areas of the county has filled up so-called “basin ponds” or land-locked ponds. These ponds have no established place to overflow, so all they can do is rise — quietly.

The rainfall of last year capped the wettest decade ever recorded in central Washington County. Last year was the wettest single year ever, with 42 inches of precipitation.

Matt Moore, administrator of the South Washington Watershed District, said that now there are three or four “extreme events” annually in Minnesota.

“We are talking about eight inches of rain in 10 hours,” he said. “This is climate change.”

In three weeks before July 14, the Valley Branch Watershed District was hammered by 15 inches of rain, according to district president Jill Lucas. That watershed runs from Stillwater to Afton along the St. Croix River.

“This is a tough, tough year,” said Lucas.

The unpredictable rains force ponds to rise randomly. County workers play a kind of Whack-a-Mole, pumping water from one pond one day, and racing to pump a lake the next.

“It’s a balancing act,” said Lake Elmo administrator Kristina Handt.

Elsewhere, officials have given up pumping — and have started buying homes to demolish them. The Valley District estimates home-buying will cost $5 million this year.

What’s the solution to the basin-pond flooding? It’s possible to build an overflow valve that flows underground.

The South Washington District this year completed a 20-year $20 million run-off project. Flood waters flow into huge basins in Woodbury and Cottage Grove, then ultimately into the Mississippi River.

Moore said the 60-acre Cottage Grove basin is 30 feet deep. Homeowners in that area, he said, don’t worry about flooding.