SOUTHWEST CLAY COUNTY – The high-hazard dam the U.S. Army Corps of Engineer plans to build through here will be about 18 feet high measured from low ground near the river, which includes 6 feet of freeboard. If the dam were to suddenly breach at maximum capacity, a wall of water 12 feet high would come rushing out.

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The potential deadliness of the dam portion of Fargo-Moorhead’s $2.2 billion flood control plan is one of the reasons Minnesota regulators oppose the project. The corps says the dam is needed to reduce flood impact on communities downstream of the diversion and is much safer than emergency levees erected during flood fights.

FARGO — As flood waters approached Rose Creek Golf Course in the spring of 2011, city workers were unrolling what was, in effect, a very long water balloon across a low-lying area near the creek.

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Nathan Boerboom, a city engineer overseeing flood control efforts, said the city wanted to test the water-filled dam to see how it would work in a real flood. The golf course was expected to flood anyway and it wouldn't have mattered if the dam failed, he said.

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As flood risks rise with climate change, many products are getting tested under realistic conditions. For example, during a 2011 flood along the Mississippi River in Memphis, the U.S. Army Corps of Engineers developed and tested a cell phone app that allowed flood fighters to respond faster to failing levees. During a 2016 flood along the Winooski River in Vermont, the University of Vermont used unmanned aircraft to produce 3D maps that helped state officials understand how they might make roads more resistant to flooding in the future.

MINOT – On the plywood sheet that blocked the door to a dark, empty house were crude words in red spray paint: "Beach party 6-22-11."

"At least my neighbors have a sense of humor," said Pat Nash as he snapped a picture. He made a chuckling sound that was half jocular and half bitter.

Nash, the owner of a trucking company, is about to become homeless as the waters of the Souris River inched toward the top of the dikes that protects his neighborhood in northwest Minot, just west of the Broadway bridge. Already it was threatening to breach dikes in various places around the city and authorities had been warning all morning that they would soon sound the evacuation siren.

RURAL VELVA, N.D. – It was a catastrophic flood that gave birth to the Souris River 11,500 years ago at the end of the last Ice Age. An ice dam containing a vast lake in southern Saskatchewan broke. The water carved a path down through Minot, then Velva, eventually making its way back north into Manitoba.

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Today, the Souris, also known as the Mouse River, is often as meek as its namesake. There is no lake threatening to inundate the valley, and the climate in the rain shadow of the Rockies or close to it is relatively dry. Still, it’s a very small river that drains an area a third the size of North Dakota.

When a lot of snow or rain falls, all that extra water will follow the river’s ancient path, and that’s where people now live, according to Steve Buan, a hydrologist with the National Weather Service office charged with forecasting river levels in the Souris Valley. “We humans, we’ve occupied that space, and Mother Nature wants it.”

LAKE DARLING DAM, N.D. – The 5 to 7 inches of rain that fell over vast plains of southern Saskatchewan and concentrated in the tiny Souris River last summer was the cause of the worst flood the Minot area had ever seen.

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In Kelly Hogan’s mind, though, it might have been a whole lot worse.

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“What if 5 to 7 inches hit Kenmare? It would’ve all come down the Des Lacs,” said the U.S. Fish and Wildlife manager.

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Kenmare is downstream of a series of dams that serves as the Minot area’s flood protection system but just upstream of the city. If torrential rain had fallen there and not in Canada, none of it would’ve been held back by dams and all of it would’ve poured into Minot.