Louisiana’s Governor Declares State Of Emergency Over Disappearing Coastline

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.

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.

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.

Here is some more info.

http://cbsd.org/cms/lib010/PA01916442/Centricity/Domain/1622...

Your link doesn't support your claim. It says region has a higher-than-average relative change. The sea doesn't rise locally, but the ground can sink downward locally.

2.) It is a combination of both. To put a number to it. 5–6 mm per year because of land subsidence and about 3 mm per year because of rising sea levels [1]. So, about 30 % is due to rising sea levels, which is pretty significant in my opinion. Especially because this effect appears to be accelerating. These numbers seem small, but their effect is devastating.

3.) I have also lived in LA for a year :)

[1] http://geology.gsapubs.org/content/43/6/519

I'm not sure how that informs you on the cause.

How I wish that were true. Many problems of humanity are very predictable - climate change is an easy one, but probably we can all think of some problems in the tech industry - and yet people do it anyway. If it were true, we wouldn't fight any wars.

> If the coastline changes were significantly caused by climate change/rising sea levels then the other Gulf coast states would have problems too.

That's not how it works. There is a lot of coastline in the world and the effect of climate change varies greatly. Look at just the East Coast of the U.S.: Miami is facing big problems; New Jersey is seeing some problems; New York is not (yet). Holland, with its low-lying reclaimed land, is likely to face problems long before the cliffs of Dover.