U.S. vulnerability to sea level rise
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
Reader Comments
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Precisely: thats why i'm watching a little area off NC/SC coast
Bertha actually formed near 30W though lol
Fully agreed there. Just because it happens once does not mean that it will happen again every year. The entire atmospheric situation is different this year compared to last.
1. Shear is generally higher this year in that area.
2. This year is neutral to El Nino, last year is La Nina to neutral.
3. SSTs are somewhat cooler in that area this year, compared to last year
Also, there are several other factors to keep in mind:
1. Bertha was a freak of nature, it was well outside the "norm" for a July hurricane
2. The GFS spins up EVERYTHING with even a 0.0001% chance. IIRC, it was spinning up Cape Verde storms back in MAY.
3. It is wayyyy too early to be looking seriously at Cape Verde storms. Yes, its possible, but it is also possible for me to grow a horn out of my head and start speaking in tongues.
While I do think that it is good to watch all parts of the tropical Atlantic for storm formation, focusing on an area near the Cape Verde Islands so early in the season is pretty senseless self-pleasure at this point. Each season is different, and if people start wishcasting or hoping for a storm to form, they are just setting themselves up for disappointment.
Thank you for the info.
Both Bertha's actually. We're not being silly, the almost exact same scenerio is setting up. GFS forecasting weeks in advance a system off CV forming in July, everyone think's were crazy to watch it, then wallabam, Category 3/4 in Early July.
Yeah, I just couldn't remember the exact coordinates
INITIAL 03/0900Z 12.6N 22.7W
And if it happens once, who could say it couldn't happen again? Just simply because its happened before makes me more inclined to watch it, because now I know it can happen.
Link
And the fact it just happened last year.
Jeff is 100% correct.... but of course you can watch it... why not? but to talk or speculate or have the "HYPE" of hoping it forms...forget about it... Cleveland will win a Championship before that happens..
1) Completely correct
2) Completely Correct
3) Completely correct
1) When Bertha happened, it was the second time it (We had a Cat 5 in July in 2005 that was CV wave lol and Bertha in 1996) occured so it obviously wasn't a freak of nature.
2) Well, that obviously wasn't the case last year, GFS got most of the storms days-weeks in advance and the GFS picked up on Bertha too. Drak always told us the GFS is not the Gospel last year.
3) Not after last year it isn't anymore.
You got to remember, we've just endured 2 wierdo seasons plus 2005 2 years before 2007.
You probably wouldve said Bertha wouldn't have formed either. But again, no one is saying this WILL form...were just watching it cause its happened before, okay?
Again lol
INITIAL 03/1500Z 13.3N 24.7W 35 KT
Wowza...
Just curious Scott do you even give it a potential to develop? I have not seen any hype on here so far not even a wishcasting landfall forecast so I'm not sure why it seems to bother you so much?
Link
What is cast in stone is that there will be a hurricane this year
cause there are noobs that browse these forums.. you get some people that post and hype up something...then that noob that was reading this goes to work and tells everyone theres a hurricane forming... and I hear that all the time.
OR
Same thing,,, people hypecast and the noobys (people who just found this site) post or just read this get overly excited or scared thinking its coming to their house. Alot of noobys that browse these forums think that most know what they're talking about.. but really 98% or more in here dont. There are a couple good forecasters/or peeps with degrees in here..but more METs dont use these forums cause for 1.... we get brushed aside by the massive amount of spam (hypecasters/wishcasters) and they never fully learn. INFACT... I have stated many times about certain things not to worry about and people just dont read or the kids-novice keep scaring up dream situations on what fantasy might happen.
Again there are a few good peeps in here and some that are learning and dont overhype or care to discuss something (cause they know).. but the whole problem is people who browse these sites dont know who really knows what their talking about.
It is 10:oo am, and the heat index is up to 96. It feels that way too.
Armpits are droolin'.
LOL extreme!
lol you sure? Its going to get that way soon enough until it goes Poof... then everyone downplays their hype!
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.
Your just a troll who wants to cause problems...we are all interested simply because Bertha formed at 25W last year, so it's happened before. No one is hyping anything/
LoL, the Browns did win when they moved to Baltimore :)
I think I define "wishcasting" differently. I define it as sticking to something developing when it is highly unlikely to develop, based on current conditions.
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.
Scott doesn't that happen though everyday with the news and local weather I went to work and people talked about the lightning storm that occurred at 5am in the morning, that was not in a blog, I have not heard anyone say a hurricane will hit because Dr.M's blog said so.I suppose someone could say that, but a savvy person would check their weather station for that.
Your right there some great bloggers on here (456, StormW) are both watching these areas so it must have some chance.
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