Thirty years ago, John McPhee wrote about this very issue. At that time a ship on the Mississippi river could go through a lock, drop FIFTY FEET, and take a shortcut to the ocean via the Atachfalaya river.
I don't think the parent comment disagrees with you that it's an emergency...I think he's surprised by the designation because it'll focus attention on the root source of the problem and make the local governments confront a not-new problem of their own making...it's a focus they may not expect or want.
> attention ... the local governments ... may not want
Having lived on the west bank, south of New Orleans, if there is anything I expect from Louisiana politicians, it's a keen pursuit of their personal, short-term self-interest. If they can each make $50,000 by dumping 50B in the Gulf, they vote "yea" before their sclerotic arteries see another hypertensive heartbeat.
Snideness aside, I agree that LA politicians are (largely) more likely to take the money and run instead of helping guide that money to where it would make a difference. One can only hope that Edwards's attitude is itself not self-interested. I think it's a reasonable hope, though, given that we've yet to see Edwards do anything nefarious* with large amounts of money despite the fact that he's seen lots of money pass through his office (e.g. with the recent flood money).
* I might be uninformed on this point. If anyone knows about some poor money-handling from his office, feel free to correct me
Can someone explain the following bit from that article to me:
"As the mouth advances southward and the river lengthens, the gradient declines, the current slows, and sediment builds up the bed. Eventually, it builds up so much that the river spills to one side."
I'm having a little trouble understanding it. What does it mean for the mouth of the river to move southward? Does sediment build up and create new land near what used to be the mouth?
> Does sediment build up and create new land near what used to be the mouth?
Yes, exactly right. This is what the entire southern coast of Louisiana is.
Envision the river like a wiggling hose spewing out water and sediment. As the sediment piles up in one area, that eventually is no longer the easiest path to the Gulf, and the hose jigs off to one side, finding a better path. When it does, it leaves behind huge, flat, fertile floodplains, bayous, and marshes. Then the new course too eventually fills up and it picks a new course again, often one of the previous ones which is now relatively more appealing.
It's been doing that for thousands of years, wandering around the southern coast of Louisiana, piling up sediment that flowed south into the great bayous and swamps.
That was until the Mississippi River became a giant trade path and New Orleans its terminus. If the Mississippi were allowed to change course and allow most of its water to reach the Gulf by going through the Atchafalaya River, the ports of Baton Rouge and New Orleans would be left dry. Meanwhile, Morgan City would be washed into the Gulf.
To prevent that, the Army Corps of Engineers has, for decades built barriers along the sides of the Mississippi to force the water to stay in that channel. Those barriers in turn reduce friction and cause the River to flow faster and faster. That means that instead of building up sediment at the current end of the river, that stuff is getting washed farther out into the Gulf.
Meanwhile, the Atchafalaya Basin and other areas which would have gotten their "turn" and had their own deltas built up have been left to erode with little new sediment coming into them.
This has been a well-known problem for longer than most of us have been alive. In the early 90s, I did a science project as a kid on it. But New Orleans has never been known for its long term planning. ("Laissez les bon temps rouler.") See also: Hurricane Katrina, which was an infrastructure failure more than a weather disaster.
So here we are.
Prediction: The only intended goal of this measure is to suck more federal cash into Louisiana which will be used to line political pockets. No real substantive ecological or infrastructure changes will come of it.
Sediment carrying capacity in water is affected by current speed. Even a slow moving river slows down when it hits the ocean. Then the sediment it is carrying settles out to the bottom.
Over time this creates an underwater mound that acts like a barrier to the current. So it deflects to one side or the other (or both). Then the sediment builds up in that new location until the current deflects again.
Over time this builds up a fan-shaped extension of the shoreline called a delta. The river might flow out through any number of channels through the delta, and it might change often.
The bigger the river, the bigger the delta. The Mississippi has a huge one... which New Orleans sits on top of.
http://www.newyorker.com/magazine/1987/02/23/atchafalaya
Just because it's not a new situation doesn't mean it's not an emergency.