River tops levee in Louisiana

AP/WWL ^ | 5/12/11

[Kartographer]

The Mississippi River has topped a levee north of Lake Providence in extreme northeast Louisiana, flooding croplands as an effort by farmers to shore up the 100-year-old structure was thwarted by the rising river.

About 12,000 acres behind the 18-mile-long levee, mostly planted in corn and soybeans, were flooding Thursday morning though no homes appeared to be in danger in the thinly populated area.

Maintenance on the levee was abandoned years ago after another, higher levee was built farther back off the river.

[dr_lew]

This Yahoo AP article, As water creeps close, residents warned: Get out does much to explain the situation at Morganza, as it mentions, "... places where there hasn't been even so much as a trickle". I think the Corps is trying hard not to kill anybody. This is putting quite a crimp in the operation, it would seem.

[abb]

I suspect the current flood is about equal to the 1927 flood in water flow, but not gauge height, as the 27 flood had many levee breaks that would have mitigated the flooding downstream of those locations.

I’m gonna see if I can find some flow numbers of the 27 flood. The science may not have been that exact back then.

[dr_lew]

I would imagine that the 1927 flood was much greater, and the apparent approach of the current flood to its dimensions is solely produced by the restriction of the modern river channel.

This idea is suggested to me by the substantial drop in the gauge height at Greenville due to the very limited release of water at Lake Providence. In 1927, the river was sixty miles wide in places, as we read. I’d love to see a MODIS AQUA image of that one.

[abb]

The “project flood” is designed for a flow rate of about 3 million ft3/sec at Red River Landing.

http://www.mvn.usace.army.mil/pao/bro/misstrib.htm

It says that is 29% greater than 1927, which would put the 1927 flood at about 2.2 million ft3/sec at that location. We’re pretty close to that flow right now.

The 1927 flood was definitely mitigated by levee failures which absorbed flow that otherwise would have flowed down the main channel.

Perhaps this flood is the 1927 equal in some locations, but not others. This one had a pretty good inflow from the Arkansas River a couple of weeks ago.

I’m still looking for flow numbers for 1927.