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southern MN | Must be behind a 20 food flood wall. Levee. Dike. Whatever you want to call it.
Water came up and over the top of the levee, and filled in th whole river basin.
In a normal year the levee prevents flooding across the river bottom. River bottoms used to be big wide marshes or wetlands or swampy at times.
Being really good land, we like to farm them, and then as long as we are farming them we want to build there too.
So we build the levees to keep the river back during high water, and enjoy that rich dirt all year long.
But the levee walls block off some of the river flow. When it rises it can’t spread out wide, so it has to rise higher to fit the same water through the levees.
Gets to be kind of a balance as to how wide apart vs how high we build levees. How much room do we leave for the river, and if we make this section narrow and high, how much does that affect those just upstream as their water gets higher too?
Over the centuries it gets worked out and everyone ends up with really tall levees.
And then we get a year for the record books every 30 years or so, and shows the places the levee wasn’t high enough or wasn’t wide enough to let all the water through - and it pops out over and back into that big wide river bottom formerly swampy area.
Moorhead MN and Fargo ND are currently sorting out how high and how wide the river channel needs to be, and how much farmland will need to be lost to make it high enough. Always some trade offs and always need to sacrifice someone else to save the ones with the most money. Farmers in the area feel it should b wide and low; townfolk think it should be high and narrow. As I understand it.
Paul
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Flood pics..
