Mississippi flooding comparison

Posted at 1:58 PM on March 28, 2011 by Bob Collins (5 Comments)
Filed under: Floods 2011

By now, perhaps, you've discovered MPR's latest blog. The Minnesota Floods '11 blog is posting updates from around the region.

I've been trying to assemble a pictorial guide to river levels with a little bit of success. When we media types throw around "flood level" numbers, it's hard to know what it means in "real life." If you live near a river, consider taking a snapshot each day (from roughly the same position) and sending it to me, documenting what time you took the picture. It'll help the project to expand the number of locations.

I started last fall with the Mississippi River as it flows through St. Paul. What I've learned is a three-foot rise in the river level to major flood stage is nowhere near as dramatic as it sounds. Here's the latest:

Raspberry Island
18.5 ft 3/28/11
15.4 ft 9/30
13.5 ft 9/29
11.3 ft 9/28
9.2 ft 9/27

Wabasha St. Bridge
18.5 ft 3/28/11
15.4 ft 9/30
13.5 ft 9/29
11.3 ft 9/28
9.2 ft 9/27

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Comments (5)

Oh, look how pretty and green it is in those pictures. I might stare at them for awhile.

Posted by vjacobsen | March 28, 2011 2:16 PM

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What is all that bright green stuff in those pictures?

Posted by Josh | March 28, 2011 2:40 PM

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Here's my question which I can't find an answer to. What does cresting at xxx feet refer to? xxx feet over what? The St. Croix crests at six hundred some feet...the Mississippi at 18. is that relative to sea level? or some point on the bottom of the river? (Obviously not in the case of the St. Croix...) How do they measure it?

Posted by Dan Gjelten | March 28, 2011 4:05 PM

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Of course a three foot rise is not that dramatic if the water stays below a levee. If current water level is one foot below the top of a levee and you have an increase of three feet from that point, the results would be quite dramatic. Many of us remember what it was like in St. Paul before the levees were raised.

Posted by David Riggs | March 28, 2011 4:15 PM

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Dan. Each river has a "historical zero" set for it. One river does not relate to another.

It's not the depth of the water. In many cases the "zero" mark is more than a hundred years ago.

In the Mississippi, "zero level" is 18.4 feet below what it is now.

On the St. Croix, zero level is 85 feet below what it is now, in Stillwater. How that relates along the river changes too. In Grantsburg right now, for example, "zero level" is only 2 above what the St. Crox is now.

What I'm not sure about is if there is only one "zero" level for the entire river. I don't think that's the case because downstream in Genoa, the Mississippi right now is at something like 630 feet.

Posted by Bob Collins | March 28, 2011 4:57 PM

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