The first two comments seem to associate anthropogenic climate change with the changes in Louisiana's coastline. A more likely culprit is hydrologic mismanagement. The coastline was formed by waterways that periodically changed channels and dumped sediment in different areas. In relatively recent times cities on the existing waterways became politically influential enough for the federal government to build a series of controls to prevent waterway changes that would otherwise distribute silt more evenly along the coastline.
Given the long-running chronic nature of the coastline change, I'm surprised this is being raised as an "emergency." Given that the principal cities of government and commerce in Louisiana would likely be extremely negatively affected by an honest root cause analysis (without the Mississippian waters, they won't work so well as ports), I'd bet the powers that be will play up climate change and ask for lots of money to be pointlessly dumped in the gulf.
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.
Exactly. Beginning with the breakup of the Great Log Jams in the 1800s, this area has been extensively hacked by humans to do something it naturally does not do.
At some point, the river is going to go back to the way it's supposed to be, Army Corps of Engineers be damned.
Agreement on the mismanagement, I grew up in NOLA. High school taught me that pretty much 50% of Louisiana's land comes from the Mississippi jumping its banks and dumping silt into a new area for a while. Once you have cities lining a river's banks there's a strong economic pressure to try and keep the river where it is, despite the slow loss of land to erosion.
I don't think it's an either-or, though. The delta's generally pretty close to sea level (NOLA averages about 5ft below IIRC) as is, and when the seas rise, that means more Gulf and less Louisiana Delta. It'll just vanish quicker because we haven't been letting the river refresh the land for a few centuries.
Ultimately it becomes a question of how much money anyone is willing to dump into this; I wouldn't be that surprised to see the city I was born and raised in become either New Atlantis or New Venice in my lifetime.
Rising sea levels due to AGW is a contributing factor[0]. Living in an area (whose economy is) also dominated by the oil industry, I understand why you and the people living in your area tend to be confused on this.
> they were able to calculate how rapidly sea level is rising with respect to the coastal wetland surface
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.
You're being condescending. Everyone in the area knows that the main culprit in losing coastline isn't AGW but the taming of the river, essentially dumping sediment that used to build the delta over the continental shelf, and all the channels cut into the marsh.
My apologies, I didn't mean to be condescending. However, It is a fact that sea level rise is a large factor in this, even if it is not the "main culprit". Most people in that area rely on the oil industry either directly through employment or indirectly through the local economy so they tend to have a blind spot when it comes to AGW, which is completely understandable.
If sea level rise were a seriously contributing factor to the Louisiana coastline problem then other Gulf coast states with similar topography (Alabama, Florida, Mississippi and Texas) would have a similar emergency. As far as I can tell, they don't to the same extent. How would you explain that sea level rise affects Louisiana more than other Gulf coast states?
Every one of those states you listed are experiencing increased coastal flooding thanks to climate change and yes that flooding damages marshlands.[0]
Nowhere have I claimed that the issue in LA is solely AGW.. only that the sizable portion of the problem that is caused by AGW is going to fall on deaf ears in that region because of the amount of oil money there.
Having lived in the area, I will attest that a significant number of locals definitely have a blind spot about oil's contribution to AGW. However, AGW is not their primary problem, nor is it something they can do much about (yes, there are things they can do, and some do them). But they, and only they, can move their local dirt around, so they're doing what they the can do.
That's my reaction: sure it makes a fine headline, but actually declaring a state of emergency has consequences that may not be appropriate. Yes, it is a common first step to receive emergency funding (I doubt that will work here, because it would require Congress to approve that funding). State laws may give the declaration more effect: does it waive regulations, give the state National Guard additional authority, etc.?
It doesn't have to be one or the other. In fact, it's likely that it's both (rising sea levels exacerbating natural delta silt deposition disrupted by dredging and loss of mangroves)
Sea levels have risen due to global warming by about 20 cm in the past century. This is most definitely one of the reasons for the receding coastline in Louisiana. They are both contributing factors.
I lived in LA for several years. Global warming is a factor in receding coastlines worldwide, but on this particular coastline it's a very small factor relative to the complete mismanagement of waterways and marsh ecosystems. As it goes on, rising sea levels will play a bigger role in a large part of Louisiana disappearing, but right now the crisis is a different man made disaster. 20cm over a century is practically nothing for a state where a good chunk of the population lives a dozen feet below sea level and a couple dozen feet below the river.
1.) 20cm is huge. You cannot build a levee system around the whole Mississippi Delta.
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.
I figured. My point is that locality doesn't inform you on whether the coastline is receding due to climate change. Do people in Los Angeles know the causes of their droughts, simply by virtue of living there?
> The first two comments seem to associate anthropogenic climate change with the changes in Louisiana's coastline. A more likely culprit is hydrologic mismanagement.
Well, I wrote mismanagement this morning and have spent more time reconsidering the topic since. I'd guess that if people knew then what they know now, they'd do things differently or not do them. Using the word mismanagement is an unfair criticism.
If the coastline changes were significantly caused by climate change/rising sea levels then the other Gulf coast states would have problems too. The link between the control humans have exerted on Louisiana rivers, additional artificial waterways and loss of coastline is fairly well established. If you'd like more information, the below medium work seems a reasonable introduction--I scanned over it and it seems to have the main points, some nice maps, doesn't avoid the problem of sea level changes, and has some human interest stuff:
> I'd guess that if people knew then what they know now, they'd do things differently or not do them.
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.
Given the long-running chronic nature of the coastline change, I'm surprised this is being raised as an "emergency." Given that the principal cities of government and commerce in Louisiana would likely be extremely negatively affected by an honest root cause analysis (without the Mississippian waters, they won't work so well as ports), I'd bet the powers that be will play up climate change and ask for lots of money to be pointlessly dumped in the gulf.