U.S. vulnerability to sea level rise

By: Dr. Jeff Masters , 4:04 PM GMT on June 23, 2009

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In the last century, sea level rose 5 - 6 inches (13 - 15 cm) more than the global average of 7 inches (18 cm) along the U.S. Mid-Atlantic and Gulf Coasts, because coastal lands there are sinking. Over 50% of the U.S. coastline is vulnerable or highly vulnerable to sea level rise, according to the Coastal Vulnerability Index (CVI) developed by the United States Geological Survey (USGS). In the U.S., relative sea level rise (the combined effects of global sea level rise plus the fact the land is sinking) is highest along the Mississippi River Delta in Louisiana, where relative sea level rises of 3.2 ft (.98 meters) have been observed during the 20th century. This is one of the highest relative sea level rises in the world. According to the NOAA Tides and Currents sea level rise interactive tool, the U.S. tide gauges that have shown the highest rates of sea level rise over the past century are at Grand Island, LA (1.8 ft rise since 1947), Galveston, TX (1.1 ft since 1957), and Chesapeake Bay, VA (0.6 feet since 1975). Alaska and some areas along the Pacific Northwest coast are at low risk of sea level rise, because the relative sea level is actually falling at present. Land in these regions is rising as it recovers from removal of the weight of the great ice sheets that covered much of North America during the last Ice Age. For example, relative sea level at Kodiak Island, Alaska has fallen by 1.1 feet since 1975, despite the fact global sea level has been increasing.


Figure 1. Twentieth century annual relative sea-level rise rates in mm/year along the U.S. coast. The higher rates for Louisiana (9.85 millimeters [mm] per year, about 3.3 ft/century) and the mid-Atlantic region (1.75 to 4.42 mm per year, 0.6 - 1.4 ft/century) are due to land subsidence. Sea level is stable or dropping relative to the land in the Pacific Northwest, as indicated by the negative values, where the land is tectonically active or rebounding upward in response to the melting of ice sheets since the last Ice Age. Image credit: Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region (data from Zervas, 2001).

U.S. Coastal Vulnerability
The Coastal Vulnerability Index (CVI) takes into account six factors:

1) The geology of the coast. Barrier islands, river deltas, and marshes are the most vulnerable to erosion and sea level rise, while steep, rocky cliff shores are the least. Sheltered bays like Galveston Bay and Tampa Bay are less vulnerable than the exposed coasts. (Note, however, that hurricane storm surges are typically higher in sheltered bays, at least for slow-moving storms).

2) How steep the land near the coast is. Gently sloping lands are the most vulnerable. In the Gulf Coast region, the slope variable has the highest risk ranking along the Louisiana coast, the Texas coast north of Corpus Christi, and the southwest Florida coast.

3) The local rate of sea level rise. The sea level is rising faster along the western Gulf of Mexico than the eastern Gulf. The highest rates of sea-level rise in the Gulf of Mexico (and in the United States) are in the Mississippi delta region (10 mm/yr, or 1 inch/2.5 years).

4) The amount of shoreline erosion going on. Most of the U.S. coast is moderately or severely eroding, and very few areas are gaining (Figure 2).

5) The mean tidal range. Shores that have a large difference between low and high tide are less likely to get a significant storm tide--the height above mean sea level of the sum of the storm surge plus the tide. For example, in a region like Maine, which has a 12 ft range between low and high tide, a storm having a 9 ft storm surge will have a storm tide below local high tide for a quarter of a tidal cycle. Shores with a very narrow tidal range (e.g., the 2 ft tidal range common along the Texas and Louisiana Gulf Coast) will get a storm tide of 8 - 10 feet with the 9 ft storm surge in the above example. Shorelines with a narrow tidal range always get high storm tides regardless of when the storm surge hits.

6) How high the waves at shore are. Obviously, shores that experience higher wave heights are at greater risk. In the Gulf of Mexico, wave energy is highest along sections of the Texas coast and on the southern tip of the Mississippi delta.

Figure 2. Shoreline change around the United States based on surveys over the past century. All 30 coastal states are experiencing overall erosion due to natural processes (e.g., storms, sea-level rise) and human activity. If the shoreline is uncolored, no data was available. Image credit: USGS, 1985, and taken from Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region).

The Coastal Vulnerability Index (CVI) web page gives detailed maps of each section of the U.S. coast, along with specific reasons why each portion of the coast was assigned the ranking it got. A brief summary:

The Gulf Coast
The Gulf Coast has 55% of its length in the "very high" or "high" vulnerability range. Fully 41% of the coast falls in the "very high" range, far more than the 28% in that category along the Pacific coast and 23% along the Atlantic coast. The region around New Orleans is the most vulnerable region of the entire U.S. coast. The Florida Panhandle, as well as the West Florida coast, are at low to moderate risk because the land is not sinking much, wave heights are lower, and the slope of the land is relatively steep near the coast. The Texas coast is considered to be at a high to very high risk because of the relatively high mean wave height, sinking land, and shallow coastal slope.

The East Coast
The East Coast has 50% of its length in the "very high" or "high" vulnerability range. The highest vulnerability areas are typically high-energy coastlines where the regional coastal slope is low and where the major landform type is a barrier island. A significant exception to this is found in the lower Chesapeake Bay. Here, the low coastal slope, vulnerable landform type (salt marsh) and high rate of relative sea-level rise combine for a high CVI value. The coastline of northern New England, particularly Maine, shows a relatively low vulnerability to future sea-level rise. This is primarily due to the steep coastal slopes and rocky shoreline characteristic of the region, as well as the large tidal range.

The Pacific Coast
The Pacific Coast has 50% of its length in the "very high" or "high" vulnerability range. Areas of very high vulnerability include the San Francisco - Monterey Bay coast and in southern California from San Luis Obispo to San Diego, where the coast is most highly populated. The highest vulnerability areas are typically lower-lying beach areas. The low risk, least vulnerable areas generally occur at rocky headlands along cliffed coasts where the coastal slope is steep, relative sea-level is falling, tide range is large, and wave energy is lower. Examples of these areas are the northern coast of Washington, Monterey, and Cape Mendocino, California.


Figure 3. The Coast Vulnerability Index (CVI) for the U.S.

References
Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region.

National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast (USGS, 2000).

Jeff Masters

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1377. KEEPEROFTHEGATE (Mod)
4:11 PM GMT on June 25, 2009
and the tunder rolls
Member Since: July 15, 2006 Posts: 168 Comments: 53285
1376. Ossqss
3:52 PM GMT on June 25, 2009
New Blog !
Member Since: June 12, 2005 Posts: 6 Comments: 8184
1375. weathersp
3:51 PM GMT on June 25, 2009
Off topic majorly..

have any of you all tried Chips that thave been in the freezer for an hour on a hot day?

You all should try..
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1374. RitaEvac
3:50 PM GMT on June 25, 2009
10AM CDT already 94 in Houston
Member Since: July 14, 2008 Posts: 1 Comments: 9628
1373. OSUWXGUY
3:50 PM GMT on June 25, 2009
GFS is definitely persistent with the African Wave. Has a tropical system develop by 48 hours... 12UTC Saturday morning. Let's see how this actually plays out!


1372. kmanislander
3:49 PM GMT on June 25, 2009
Back later
Member Since: August 19, 2006 Posts: 0 Comments: 15687
1371. weathersp
3:49 PM GMT on June 25, 2009
Quoting Patrap:
GOM 84 Hour Wind Forecast Model


Good Link..Thanks Pat! saving that one..
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1370. Patrap
3:44 PM GMT on June 25, 2009
GOM 84 Hour Wind Forecast Model
Member Since: July 3, 2005 Posts: 419 Comments: 127358
1369. CybrTeddy
3:43 PM GMT on June 25, 2009
Area of Interest 1: MLC with gaining convection in Caribbean.

Area of Interest 2: Strong Cape Verde wave.
Member Since: July 8, 2005 Posts: 259 Comments: 23492
1368. RitaEvac
3:43 PM GMT on June 25, 2009
Member Since: July 14, 2008 Posts: 1 Comments: 9628
1367. IKE
3:42 PM GMT on June 25, 2009
12Z GFS at 36 hours....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
1366. stoormfury
3:40 PM GMT on June 25, 2009
broad area of low pressure in the GOMEX. within this area are a number of mid level votices spinning around. convection has been on the increase as the system appers to be drifting to the southwest. shear is only marginal, but is expected to be very favouable the next 72 hrs. there are no evidence to suggest that the the mid levl vortices are working down to the surface. before that happens the convection has to coalesce to one area of heavy convection. this area should be quite interesting the next few days
Member Since: August 22, 2006 Posts: 0 Comments: 2571
1365. weathersp
3:30 PM GMT on June 25, 2009
Quoting Ossqss:


Can you grab the 26 depth, I cannot get connected, big brother stepped on it.

Member Since: January 14, 2007 Posts: 17 Comments: 4140
1364. Ossqss
3:29 PM GMT on June 25, 2009
Quoting weathersp:


Can you grab the 26 depth, I cannot get connected, big brother stepped on it.
Member Since: June 12, 2005 Posts: 6 Comments: 8184
1363. futuremet
3:28 PM GMT on June 25, 2009
GFS 10m wind forecast 06z


Quite a forecast
Member Since: July 19, 2008 Posts: 43 Comments: 4051
1362. AussieStorm
3:26 PM GMT on June 25, 2009
Quoting BahaHurican:
Well, it's getting to be that time of century again. . . lol
-----------------
Hey, Aussie. How cool has it gotten?

well it was 5C here this morning and it got to a balmy 15C today. but at least the sun was out. Currently its a whole 9C and its ment to get down to 5C again tonight. Glad i got my electric blanket.
Member Since: September 30, 2007 Posts: 9 Comments: 15892
1361. BahaHurican
3:25 PM GMT on June 25, 2009
Later, all. Gotta head 2 wk.. . .:o(
Member Since: October 25, 2005 Posts: 19 Comments: 21169
1360. weathersp
3:25 PM GMT on June 25, 2009
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1359. BahaHurican
3:23 PM GMT on June 25, 2009
Quoting DestinJeff:


little bit closer to home than the "pre-CV system" (somebody will call it that)... i'll keep my eyes on the carrib for now, despite the universal disdain for the NAM
Even if not a truly tropical entity, it could be a rainmaker for the area.
Member Since: October 25, 2005 Posts: 19 Comments: 21169
1358. weathersp
3:22 PM GMT on June 25, 2009
Quoting DestinJeff:


... cue the "going to pull a Dolly" posts

btw... Ana Montana, Ike? Really? have you no shame?


Is there way I can click "like this comment" more than once? LOL
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1357. BahaHurican
3:21 PM GMT on June 25, 2009
Quoting hurricane2009:


Its only happened twice 1907 and 1914
Well, it's getting to be that time of century again. . . lol
-----------------
Hey, Aussie. How cool has it gotten?
Member Since: October 25, 2005 Posts: 19 Comments: 21169
1356. Ossqss
3:20 PM GMT on June 25, 2009
TCHP is very ripe in that area Kman. The site is too slow to post it, at least from this PC.
Member Since: June 12, 2005 Posts: 6 Comments: 8184
1355. OSUWXGUY
3:18 PM GMT on June 25, 2009
Quoting kmanislander:


I do indeed. We won't have long to wait to see how it plays out. The NAM has been developing a 1004 mb low in the NW Caribbean late this weekend for several runs now.


Hey Kman! Agreed...something else to keep an eye on...especially with ALL models showing low shear in that area.
1354. kmanislander
3:17 PM GMT on June 25, 2009
Quoting DestinJeff:


little bit closer to home than the "pre-CV system" (somebody will call it that)... i'll keep my eyes on the carrib for now, despite the universal disdain for the NAM


The 12Z NAM has a 1004 mb low near the Yucatan on Saturday. For that to materialise things would have to get going quickly near Nicaragua.
Member Since: August 19, 2006 Posts: 0 Comments: 15687
1353. IKE
3:16 PM GMT on June 25, 2009
Quoting DestinJeff:


... cue the "going to pull a Dolly" posts

btw... Ana Montana, Ike? Really? have you no shame?


LOL.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1350. beell
3:15 PM GMT on June 25, 2009
Quoting jeffs713:

I completely agree there. I watch every wave, but I do my best to avoid hyping up anything to possibly form, unless it is very close to the US coast, and may be a "homegrown" system.

All that said... my apologies if I offended anyone by accusing them of wishcasting or anything like that. Its still morning here.


Certainly no offense here, jeffs. And if anyone needs some help keeping up with the waves-and they do get a little indistinct at times, these folks have been including a small section in their Monday through Friday discussion dedicated to analyzed tropical waves and forecasted movement out to 84 hrs.

Looks like this for yesterday: (if anybody knows how to paste text and keep the format-please advise lol).

EASTERLY/TROPICAL WAVES (INITIALIZED AT 12Z TODAY)

INITIAL F24 F36 F48 F60 F72 F84

50W (S/13N) 53W 57W 60W 63W 65W 69W
67W (SURGE) 71W 74W 76W 79W 81W 82W
78W (S/18N) 81W 83W 85W 88W 90W 92W
Caribbean Discussion-International Desk
Member Since: September 11, 2007 Posts: 141 Comments: 16121
1349. weathersp
3:14 PM GMT on June 25, 2009
Quoting kmanislander:
Eastern GOM

South central Caribbean


Shear is only 5-10 kts there too..
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1347. BahaHurican
3:12 PM GMT on June 25, 2009
Quoting beell:
Couple of other things.
If you are are not making an attempt to follow each and every wave from Africa clear through to the EPAC, then you are not "watching" the tropics. W456 comes to mind...

There is almost as much to be learned by why something did NOT form.
Well said. Point of blogging on this topic is to see what can be learned by WATCHING, not by existing on past experience. I'm the 1st to go look at old charts & stuff, but they're not the REASON I blog. It's looking at every "blob" and trying to understand the processes that influence its [non]formation.

Member Since: October 25, 2005 Posts: 19 Comments: 21169
1346. IKE
3:11 PM GMT on June 25, 2009
Ana Montana?
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1345. atmoaggie
3:09 PM GMT on June 25, 2009
Quoting hurricane2009:


That is for the season as a whole, there will be episodes of heavy dust yes, but just not as numerous


Not talking about that. Someone pointed out this plot with a lot less dust/dry air on it last week, as well.

One day's plot is not a season.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
1344. kmanislander
3:09 PM GMT on June 25, 2009
Quoting DestinJeff:


i think much of the reason everyone says to ignore it is simply because everyone says to ignore it.... know what i mean?


I do indeed. We won't have long to wait to see how it plays out. The NAM has been developing a 1004 mb low in the NW Caribbean late this weekend for several runs now.
Member Since: August 19, 2006 Posts: 0 Comments: 15687
1342. AussieStorm
3:07 PM GMT on June 25, 2009
Evening all..... what's the latest?
Member Since: September 30, 2007 Posts: 9 Comments: 15892
1341. BahaHurican
3:07 PM GMT on June 25, 2009
Quoting RitaEvac:


What is cast in stone is that there will be a hurricane this year
Even this isn't cast in stone. It's possible to have a season without a 'cane.
Member Since: October 25, 2005 Posts: 19 Comments: 21169
1340. kmanislander
3:07 PM GMT on June 25, 2009
Eastern GOM

South central Caribbean

Member Since: August 19, 2006 Posts: 0 Comments: 15687
1338. NRAamy
3:03 PM GMT on June 25, 2009
My Local Weather:
John Wayne-Orange County, California
64 °F
Haze
Member Since: January 24, 2007 Posts: 317 Comments: 31946
1337. Ossqss
3:00 PM GMT on June 25, 2009
Opinions are like Belly Buttons…
Member Since: June 12, 2005 Posts: 6 Comments: 8184
1336. CycloneOz
2:58 PM GMT on June 25, 2009
Quoting Tazbeat:


What if someone else told you you HAD to put your seatbelt on because if you didn't, you could die in a crash that COULD happen to you on this trip?


I am told I have to wear a seat belt from someone I've never even met. And if I don't and get caught I get ticketed.

How in the world did the five of us kids survive Dad's crazy driving in the back of that station wagon?

I resent being told to wear a seat belt.

Next thing...they'll tell me I can't eat fast food anymore, either.

Life in America...it ain't what it used to be, folks. You've lost a ton of liberties...and you will continue to lose them.
Member Since: August 26, 2006 Posts: 10 Comments: 3616
1335. kmanislander
2:57 PM GMT on June 25, 2009
1323 and 1324

Let's see if this vorticity works its way over to the Nicaragua coast from the South Central Caribbean

Member Since: August 19, 2006 Posts: 0 Comments: 15687
1334. atmoaggie
2:55 PM GMT on June 25, 2009
Yay rain. We if we can get a little more, just without the tree-felling gusts this time, please.

Member Since: August 16, 2007 Posts: 6 Comments: 12461
1333. CycloneOz
2:54 PM GMT on June 25, 2009
Sure...it's a longshot, but if that wave or energy-ladened remnants of it survive long enough for a move into the eastern Caribbean...

...then all bets are off.

100% of us will not only be watching, but deeply caring what this system does.

Member Since: August 26, 2006 Posts: 10 Comments: 3616
1331. weatherblog
2:53 PM GMT on June 25, 2009
Quoting CybrTeddy:
I guess this an example of hype then lol.


INITIAL 04/0900Z 22.7N 55.8W 125 KT
12HR VT 04/1800Z 23.5N 57.7W 125 KT
24HR VT 05/0600Z 24.0N 60.2W 115 KT
36HR VT 05/1800Z 24.0N 62.6W 110 KT
48HR VT 06/0600Z 23.4N 64.9W 110 KT
72HR VT 07/0600Z 22.5N 69.5W 115 KT
96HR VT 08/0600Z 23.0N 73.5W 115 KT
120HR VT 09/0600Z 25.0N 76.5W 115 KT


Better to be prepared than to wait and do nothing until right before the storm hits.
No one is saying they think 100% this will develop, I give it a 30-40% actually, because of the conditions and that we've seen so many waves go poof as soon as they hit the water.


Geez, that's not funny! That had it right over my house. Glad that didn't actually materialize.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
1330. jeffs713
2:53 PM GMT on June 25, 2009
Quoting beell:
Couple of other things.
If you are are not making an attempt to follow each and every wave from Africa clear through to the EPAC, then you are not "watching" the tropics. W456 comes to mind...

There is almost as much to be learned by why something did NOT form.

I completely agree there. I watch every wave, but I do my best to avoid hyping up anything to possibly form, unless it is very close to the US coast, and may be a "homegrown" system.

All that said... my apologies if I offended anyone by accusing them of wishcasting or anything like that. Its still morning here.
Member Since: August 3, 2008 Posts: 16 Comments: 5869
1329. Tazbeat
2:52 PM GMT on June 25, 2009
Quoting zoomiami:
The flip side of the evacuation argument is that it only takes just one.

We use to have to prepare a lot more for storms before they were able to track as well as they can now. Our theory then, and still is today, is better to be wrong 9 times, and right once. We put our seat belts on every time we get in the car in case we have an accident - how often does it actually happen?



Believe me, I fully understand the purpose behind the principle. But the difference is, when you put your seatbelt on, that's your choice. What if someone else told you you HAD to put your seatbelt on because if you didn't, you could die in a crash that COULD happen to you on this trip? And it didn't happen. How often would you listen to that person before you stopped listening - just in time for the REAL accident?
Member Since: June 13, 2009 Posts: 0 Comments: 8
1328. atmoaggie
2:52 PM GMT on June 25, 2009
Were we not talking about reduced dust in the MDR last week...looks like it recovered to me.


(click for full size)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
1327. CycloneOz
2:50 PM GMT on June 25, 2009
Quoting RMM34667:
cool picture from cape cod..

In Chatham, an austere utopia yields to a relentless tide


Link


That pic is just way too cool! I love those shots at wave level! :)
Member Since: August 26, 2006 Posts: 10 Comments: 3616

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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