Monday, April 25, 2011

River Levels to Bust Cairo's 1937 Record Next Week

It's official, the river forecast for Cairo will surpass the record 1937 flood level.

I've been wondering if the AP had the wrong information and now it seems to be confirmed. There have been a number of reports that the river would "crest" Friday a foot below record stage at Cairo. The charts I was looking at from the NWS didn't show a crest, just the last point in the forecast Friday.

According to the Ohio and Lower Mississippi River Forecast on another page from last night at 7:40 p.m., the Ohio River expected to crest (meaning its highest point) will be on May 3, a week from Tuesday, at 60 feet which is a half a foot below the all-time record of 59.5 feet set on Feb. 3, 1937.

One of the important things to notice about the first chart is the difference between what was actually measured this afternoon and what was forecasted. The actual measurement was higher than the forecast. That's not good.

Unlike the 1937 flood which started upstream on the Ohio and came down to an only moderately flooded Mississippi, this one is appears to be due to heavy rains here in the Midwest with both major rivers in flood stage. Upriver on the Ohio is not so bad.

Paducah is expected to see a crest of 55 feet on the 3rd as well which will surpass all records except the big one of '37. That year it was 60.6 feet. While that's still major flooding for lands outside the levees, it's not at the point that would normally impact the heavy industries upstream at Calvert City, Ky. It's also well below the levee height of 64 feet.

A key note to last night's flood forecast by the NWS. They based it on 48 hours of future rainfall rather than the normal 24 hours. "River sages may potentially be 1-3 ft higher in some areas with 5 days of future rainfall."

That doesn't give a whole lot of wiggle room for Cairo. The expected 60 foot crest is just four feet below the top of the levees protecting Cairo.

Upriver Mounds and Mound City have another foot of protection. Their levees don't get topped until the river at Cairo is 65 feet.

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