NewsLouisiana Flooding


The Morganza gates open Sunday, that’s just the beginning

Posted at 8:49 AM, May 29, 2019
and last updated 2019-05-29 10:28:40-04

It’s been a week now since the Army Corps of Engineers announced the possibility of opening the gates at the Morganza Spillway.

Since then there have been countless stories, articles, videos, etc. dealing with the Morganza and the possible fall out.

These stories are likely going to continue since there’s no telling how long the gates will have to stay open, or how long it’ll take for the water to clear out and into the Gulf of Mexico.

While the levels are already high and warrant the opening of the gates, we haven’t even seen all the water reach Louisiana yet.

So lets talk about why this will take so long and why it’s likely that we’ll still be talking about the Morganza in late June/early July.

Reports of moderate to major flooding along the Arkansas and Mississippi Rivers.

As mentioned earlier we are already dealing with close to record levels here in Louisiana and just glancing up river there is still a lot of water on the way.

Major flooding has been reported on the upper sections of the Mississippi in Iowa, Missouri, and Illinois after an already high river and a deluge of recent rainfall.

It takes weeks for that water to arrive, the Mississippi is often discussed as a slow meandering river so rainfall in Iowa won’t arrive in Louisiana for quite some time.

Major flooding along the Arkansas River.

Compounding the problem is the major flooding along the Arkansas River which runs through north Oklahoma through Arkansas, and spills into the Mississippi south of Memphis.

After flooding rain fell in north Oklahoma and southern Kansas over the last week that river is also running incredibly high.

In fact the Keystone Dam which holds a lot of that water back has been forced to open releasing another tremendous amount of water into the Mississippi.

Keep in mind that this water doesn’t arrive overnight, this again will take weeks to reach the Mississippi River, and another several weeks before it races through the gates of the Morganza.

Which brings us to the opening of the gates and the diversion of water from the Mississippi into the Atchafalaya Basin.

The Army Corps of Engineers is planning for a slow controlled approached to the opening, starting with one (out of 125) gate opening and gradually increasing over several days.

This is not going to be a wall of water busting loose and racing down the spillway, this is trying to fill an Olympic sized swimming pool with a garden hose (courtesy Dave Baker for the metaphor).

Chart of the river rise along the Atchafalaya River in 2011.

While 2011 is a perfect comparison (more on that later) it is one of only two different data points we have to look at since this is only the third time the gates have opened.

The river gauge at Butte La Rose in 2011 was close to 20 ft when the gates opened (the readings this year are in similar territory) and notice how long it takes for the river to crest.

Gates opened May 14th, 2011 and you really don’t notice a major rise in the river until a week later, and it took two weeks after the opening for the river to crest.

Now as mentioned above, this isn’t a perfect comparison in 2011 the ground was a lot dryer then and the ground was in a better place to hold water.

This year we also have the water from the Arkansas River, from Little Rock to Tulsa the river is expected to break records for high water marks.

These records go back to the 1940s and when glancing at the numbers from 2011 those numbers don’t even register as a top ten event.

All of this water will make for a prolonged event as water can only go so fast through the basin and out into the Gulf of Mexico.

So when the gates open Sunday it shouldn’t been seen as the end of an event, but merely the beginning.