Flooding Q&A

Obligatory photo taken from the overlook at Trail of Tears State Park

Although we're not entirely out of the woods yet, the river is receding at a steady clip at Cape Girardeau, so hopefully we'll soon be able to return to our regularly scheduled discussion of snowstorms. In the meantime, here are some answers to questions that you might have about the flooding.

How much higher did the river get versus the record?

At Cape Girardeau, the previous record high stage was 48.49 feet set Aug. 8, 1993. This time, the river reached 48.86 feet at 10 PM on Jan. 1.

That's a difference of 0.37 feet, or 4.4 inches. The forecast had called for the river to potentially touch 50 feet on the gage, but a levee failure south of Thebes helped keep the river from rising any more.

At Thebes, the previous record was set on May 23, 1995, at 45.91 feet (this was a few inches higher than in 1993). The river touched 47.74 feet at 1:30 AM on Jan. 2 before suddenly dropping in response to the downstream levee breach. So, the record at Thebes was broken by 1.83 feet.

Was the Cape floodwall in any danger?

Not really. Even if the river had reached the highest forecast stage of 50 feet, the water would still have been 4 feet below the top of the wall, which would have left plenty of freeboard to block waves from splashing over.

In the aftermath of the 1993 flood, the Southeast Missourian published a story describing the floodwall. The story included this quote from "Andy" Juden Jr., chairman of the levee district: "There is no reason to have any concerns about the seawall. Actually the wall gets stronger as the river goes up. There is a footing for the wall that goes way out into the river. The weight of the water adds to the structural integrity of the wall."

If we were to face an even greater flood in the future, Cape would still be protected because other levees up and down the river would fail long before the water reached 54 feet.

How much water was flowing past Cape at the crest?

The gage information on the National Weather Service website provides flow data, as measured in kcfs, or thousands of cubic feet per second. However, we went "off the chart" during the worst of the flooding, as the website stopped reporting flow values once the stage hit 47.85 ft. At that point, the last recorded flow was 1,050 kcfs, or 1,050,000 cubic feet per second.

One cfs is equal to 448.8 gallons per minute, so the river was pushing over 471 million gallons per minute past Cape. Or 678 billion gallons per day!

The usual cliche in these situations is to measure water volumes in terms of Olympic-sized swimming pools. According to Wikipedia, such a pool holds approximately 660,000 gallons, so the river was capable of filling 714 Olympic-sized swimming pools per minute.

But remember these numbers are from before the crest, when the river was a foot lower. It'll be interesting to see if official flow numbers are later published once scientists have a chance to study the aftermath of this flood.

Was the flooding visible from space?

Thanks to the clear skies this weekend, NASA satellites were able to clearly capture the extent of the flooding. The University of Wisonsin-Madison website offers false-color imagery near the peak of the flooding. In addition to the obviously swollen Mississippi and Ohio rivers, the satellite view picked up on the backwaters in the Diversion Channel, Apple Creek, and even Indian Creek near Trail of Tears State Park.

How rare is winter flooding?

According to the list of historic crests for Cape Girardeau, only one other December or January event cracks the top 30: a 35.9 ft. crest on Jan. 8, 2005. That barely even counts as a flood.

Most major floods in the modern era have occurred during the spring (1973, 1995, 2011) or summer (1993).