Mississippi River Flooding 2011 – April Update

UPDATE: Mississippi River Flooding – May 2011 Update

The rainy season is in full swing here in the Midwest. Rain is constantly in the air and in the forecast, and a particularly strong thunderstorm last night led to some “tornadic activity” that blew part of the roof off St. Louis’s Lambert Airport and even closed down part of I-70 for a bad part of the evening, probably due to downed power lines – at least that’s what I got searching for chatter about “I-70″ on Twitter.

[Although for those of you finding this page by searching things like "is i-70 over mississippi river flooding" the highway is most definitely completely open at this time! The I-70 bridge is so much higher than the river that it didn't close during the record '93 flood and we've still been several feet below that this year. If you're at all concerned about closed roads in Missouri, please check MODOT's map.]

I’ve been watching the river levels after every rainfall, and the Mississippi is rising. The gage in Winfield, MO, near my parent’s home, is already predicted to crest only four or five feet shy of where it crested in July 2008, so I thought it’d be a good time to take a snapshot of the conditions along the river.

The following picture gives a list of where 2011 ranks among the years for records of historical crests at various points along the Iowa/Missouri/Illinois border, as listed by the National Weather Service at the link above. This is a highly unscientific chart, as some of the gages seem to have records that go much farther back than others, and in 2011 some of them have already crested from the latest storms, some are about to crest, and for some farther down have we don’t yet know where they will crest. But this is still a good, rough idea:

This map covers Iowa and Missouri. The worst the Mississippi River has done so far is rank 4th – only beat by 1965, 1993, and 2001 in upper Iowa. But this year has not (yet?) beat 2008 farther down in Iowa and into Missouri. Why does Keokuk jump down to 16th? Well when you click “Historical Crests” on the website, some stations have records only going back into the 50′s and 60′s, and some have records going back into the 1800′s. For the main part of Iowa and Missouri, this looks like the type of flood that comes around every 5 years or so – maybe one of the top 10 in the last 50 years. This type of flooding is a little rarer farther upstream, where it’s pushing top 5 in the last 50. Farther downstream, where the river is used to collecting all the rainwater from the northern states, 2011 looks pretty unremarkable thus far. If the river crests in downtown St. Louis where it’s currently predicted, it will be 4 feet shy of the 2008 level, which itself ranks 13th place. The water level down at Cape Girardeau is still rising with no predicted crest as of yet, but it may wind up between 10th and 20th.

But it’s only April. 2008 reached its crest at most stations at the end of June or the beginning of July. The 1993 flood, which still holds most records along the river, didn’t crest until August 1 at the St. Louis Arch. At the same time, if you look at the lists of historical crests, a lot of them seemed to have happened at the end of April – just like this one – or throughout May and June. In other words, it’s all going to depend on how much more rain we get. So maybe this kind of flooding comes along every 5-10 years, and it’s only another percentage of those floods that get enough rain to maintain that level and push even higher. We’ll see what happens in May. I’ll be watching…