Morganza watch party

There's an historic event going on out there.

Flooding in at least 8 states along portions of the Mississippi River – due to relentless, record-breaking spring rainfall – is the longest-lasting since the "Great Flood" of 1927, the National Weather Service said.

The 1927 flood, which Weatherwise magazine called "perhaps the most underrated weather disaster of the century," remains the benchmark flood event for the nation's biggest river.

Anytime a modern flood can be mentioned in the same breath as the Great Flood is newsworthy: During that historic flood, hundreds of thousands of people fled their homes as millions of acres of land and towns went underwater.

Sunday, everyone will be glued to their live streaming devices to watch the Corps of Engineers pop open the Morganza Spillway for only the third time ever.  In 2011 this was quite a spectacle so gather around and... oh.. well they're gonna do it slowly this time.

Engineers plan to open one flood gate per day for the first three days to allow the water to slowly flood into the spillway. They're aiming for a one foot rise each day during that period to allow animals in the area to safely flee. After that, they'll likely open up 20 to 25 of the system's 125 gates.

Well, okay, if we have to give up a bit of the show for the sake of some fleeing animals, I guess that's the sort of trade we have to make.  Safety first.  Oh also in that vein, please remember to secure your basketball players before the spillway opens.

At its peak, the water in parts of the Morganza Spillway will be high enough to cover professional basketball players.

The U.S. Army Corps of Engineers predicts up to 7 feet of inundation in the spillway around Krotz Springs after the Morganza opens Sunday, said David Ramirez, chief of water management for the Corps’ New Orleans district.

As long as we're measuring wetlands loss in football fields, we can do river flood depths in these units.  It makes as much sense.

Anyway the real reason I'm even posting this today is so I don't forget to mark these Jeff Masters posts about the Old River Control Structure that went up at Weather Underground last week. There are three of them. Here are the links with key excerpts.

Part 1: America's Achilles' Heel: the Mississippi River's Old River Control Structure

The mighty Mississippi River keeps on rollin' along its final 300 miles to the Gulf of Mexico south of New Orleans—but unwillingly. There is a more attractive way to the Gulf—150 miles shorter, and more than twice as steep. This path lies down the Atchafalaya River, which connects to the Mississippi at a point 45 miles north-northwest of Baton Rouge, 300 river miles from where the river empties into the Gulf of Mexico southeast of New Orleans.

Each year, the path down the Atchafalaya grows more inviting. As the massive amounts of sediment the Mississippi carries—scoured from fully 41% of the continental U.S. land area, plus a portion of southern Canada—reach the Gulf of Mexico, the river's path grows longer. This forces it to dump large amounts of sediment hundreds of miles upstream, in order to build its bed higher and maintain the flow rates needed to flush such huge amounts of sediment to the sea. Thus, the difference in elevation between the bed of the Mississippi and the Atchafalaya—currently about 17 - 19 feet at typical flow rates of the rivers—grows ever steeper, and the path to the Gulf down the Atchafalaya more appealing.

The two highest floods on record at the Old River Control Structure occurred in 2011 and 2019, and the 2018 flood ranked as the fourth highest on record. Floods like these further increase the slope, as flood waters scour out the bed of the Atchafalaya. Without the Old River Control Structure, the Mississippi River would have carved a new path to the Gulf in the 1970s, leaving Baton Rouge and New Orleans stranded on a salt water estuary, bereft of their main source of fresh water to supply their people and industry.

Part 2:  Escalating Floods Putting Mississippi River’s Old River Control Structure at Risk

In Beyond Control: The Mississippi River's New Channel to the Gulf of Mexico, historian James Barnett Jr.’s fantastically detailed 2017 book, he brings up a possibility that other experts have also warned about: while the Old River Control Structure is the most likely place for the river to break through and carve a new path to the Gulf, the river could also breach its levees elsewhere and accomplish the same feat. One possible location for such a breakthrough: Widow Graham Bend, the location of a sharp meander bend in the river about thirteen miles north-northwest of the ORCS. This location was identified as early as 1882 as a possible location where the Mississippi could breach its west bank levee and send its waters southward to join with the Atchafalaya River (though it would also have to break through a second levee that lines the Red River).

The river did breach the levee at Widow Graham Bend during the great flood of 1927, but the Mississippi was not ready to jump to a new channel then. Since the flood of 1927, the critical west bank levees near the ORCS have been built to a height of 71 – 74 feet--at least seven feet higher than the all-time record flood from 2011.

Part 3:  If the Old River Control Structure Fails: A Catastrophe With Global Impact

Failure of the ORCS and the resulting loss of barge shipping that might result could well trigger a global food emergency. The U.S. is one of the world’s largest exporters of grain, and 60% of that grain is transported to market by barges travelling on the Lower Mississippi River. A multi-month interruption in the supplies of more than half of U.S. grain to the rest of the world can be expected to cause a spike in global food prices, and potentially create dangerous food shortages in vulnerable food-insecure nations.

As I wrote in my 2016 post, Food System Shock: Climate Change's Greatest Threat to Civilization, the greatest threat of climate change to civilization over the next 40 years is likely to be climate change-amplified extreme droughts and floods hitting multiple major global grain-producing "breadbaskets" simultaneously. An interruption in U.S. grain exports due to failure of the ORCS, if it occurs during the same year that another major grain-producing nation experiences a serious drought or flood, could cause a frightening global food emergency. The impact might be similar to what was outlined in a "Food System Shock" report issued in 2015 by insurance giant Lloyds of London, with rioting, terrorist attacks, civil war, mass starvation and severe losses to the global economy.

Just a few things to think about while you're watching them pull open the first bays on Sunday.