Monday, March 23, 2009

Flooding of the Minnesota River

There is a lot of rain falling.

Much of it in the very large drainage basin of the Minnesota River.

To understand the Minnesota River and its tributaries (and their very unique geography.)


I would recommend you go read the entire report and newsletters at The River Warren Research Committee {RWRC}

The only waterfall on the Mississippi River is in Minneapolis... The Falls of Saint Anthony, where the Mississippi River falls into the huge valley carved out of the countryside by the monstrous and now extinct Glacial River Warren.

(extinct rivers are identified by placing the word "river" first, before the name as in: "River Warren".)

All the tributaries of the Minnesota River (which lies entirely on the bottom of the big ditch dug by the River Warren) must fall some 200 feet to reach the Minnesota.

In the process they expend a lot of kinetic energy which makes for highly incised river valleys cutting into the glacial till, especially in high water events.

Look at the Cottonwood, Redwood, Yellow Medicine, Watonwan, Le Sueur, Pomme De Terre, Chippewa, Lac Qui Parle and all the other tributary streams to the Minnesota river. [and Mid-Mississippi for that matter]

All experience the big drop and are in steep valleys with highly erodible stream banks of glacial till and gravel.

The Blue Earth River is a very unique example, with FIVE sub-tributaries cutting inland and upstream, and coming together all at once at Mankato.

Read all about it at...

Due to their "underfit" nature at the bottom of the River Warren Valley, the Minnesota and the (middle) Mississippi River are naturally flood prone, sediment-laden streams with wildly fluctuating water levels.

The Mississippi has the Lock and Dam system which provides "flood-flattening".
In the fall/winter, water is released to allow room for the spring snowmelt and rains.

This lengthens the duration of, but reduces the level, of the crest.

Dams can prevent flooding, sedimentation, aid navigation and generate electricity.
They also raise property values along the riverfront with a more stable elevation MUCH less prone to large fluctuations.

Farmers are not the reason the Mississippi and Minnesota Rivers flood, no matter what they tell you at the MPCA, DNR, Board of Water and Soil Resources [BWSR], Legislative Commission on Minnesota Resources LCMR, the Land Stewardship Project, or any number of Environmental Agencies and government fortified "non"-profit organizations.

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