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Friday, October 2, 2009

What Happens When The Sea Level Rises?

Do you live near the beach? You might want to pay attention to the maps in this article. Do you want to live near the beach? You too might want to pay attention to the maps here!

At a recent climate conference in Oxford, several climate experts predicted that a rise in sea-levels of at least 2 meters is almost inevitable. More interestingly, if current trends hold, sea-levels might rise by 5 meters or more over the next couple of centuries.

So, what happens when sea-levels rise by several feet. Coastal areas get swamped by sea water, obviously. How much coastal land is susceptible to being submerged by a rise in sea-level?

It is an interesting question. So interesting, in fact, that the good folks at the University of Arizona, Tucson, have already done the research to answer it. Here, in their own words, is what they did to study the issue and come to their conclusions:

Using digital elevation models (DEMs) available through the United States Geological Survey (USGS), we calculated coastal areas susceptible to sea level rise based solely on elevation and adjacency to the sea for regions around the globe (Weiss and Overpeck, in preparation). Data from the Global 30 Arc-second Elevation Dataset (GTOPO30), which offer a global DEM with raster resolution of approximately one kilometer, were used for global analysis. Shorelines are an inherent feature in this dataset. For Puerto Rico and selected subregions of the United States, data with raster resolution of 30 meters from the National Elevation Dataset were utilized. At the time of data retrieval, this dataset contained Puerto Rico, the conterminous United States, Hawaii, and Alaska. Coverage of American Samoa has since been added. As shorelines are not defined in this dataset, vector shoreline data from the NOAA Coastal Services Center were obtained, converted to raster format, and employed in defining shorelines. We created an algorithm for application in geographic information system software in order to perform a cell-by-cell analysis of DEMs, determining for each cell whether or not its value (i.e., elevation) is less than or equal to a particular integer and, if so, whether or not this cell is adjacent or connected to the sea by cells of equal or lesser value. The algorithm was applied for integer values from one through six to reflect our goal of determining areas susceptible to sea level rise of one to six meters.

Based on these studies, they have created an incredible program that actually shows the effect of rising sea-levels by dynamically generating maps based on user inputs. You can access the viewer for the entire globe here. You can also get a higher resolution viewer for just the contiguous USA, Puerto Rico and US Virgin Islands here.

Their website also has some very interesting static maps of the individual continents and the effects that various levels of sea-level increase will have on the coastal areas of these continents. Obviously, the research takes into account only the rise in sea-level and not other effects that could accompany it, such as different current patterns, changes in sedimentation and erosion, etc., that can cause the land area in danger to be dramatically different. These maps do provide a first-level look at what the possible danger areas are so that more effort can be expended in preparing these areas.

I have taken the liberty of taking some of their images and combining them into animated GIF images that show the effects of rising water levels in an interesting, graphical way that allows the human mind to see the incremental submersion more naturally than by looking at a bunch of static images. If you are interested, I used a software called GIF Construction Set Professional to generate these images from the original static images.

Even if you don't believe all the rhetoric that comes out of the global-warming or climate-change (or whatever the term-du-jour is) camps, it may be a good idea to study these maps carefully and make some cheap real-estate investments. If you plan it carefully, you might get beach-front property for a fraction of what it would be worth sometime in the future!

P.S.: For some reason, the animations work sometimes and at other times, they get stuck at one of the images from which the animations are constructed. I have grown tired of trying to debug the problem after reading dozens of articles on how to make animations work with blogger. If you are not able to see animated images, right-click on the images and choose Save Image As. Save the images on your desktop, and open them with a good image viewer like IrfanView that supports animated GIF's. The animations always seem to work locally, but not reliably inside blogger. Note that MS Paint does not support animated GIF's (you will only see the first image, no animation).

North America
North America

The most obvious impacts are in Florida and along the gulf coast (these effects are better illustrated in the detailed maps devoted to these parts of the US). But there are pretty serious effects all along the east cost too. San Francisco bay is impacted on the west coast. And there are isolated impacts in Alaska and the arctic coast of the continent.

Florida
Florida

As can be expected, even moderate increases in sea-level are pretty devastating for southern Florida. Miami and the everglades are well under-water before the sea-level rises even 2 meters. But I was surprised that even places like Orlando, quite far from the coast are seriously impacted by higher rises in sea-level.

Louisiana
Louisiana

Given that most of southern Louisiana is at or below current sea-level, it is not surprising that the impact on this part of the world is immediate and profound even with a 1-meter rise in sea-level. Most of the lakes close to the sea-shore would be inundated and become part of the sea due to this sea-level rise also.

Northeast US
Northeast US

Most of the impact along the atlantic coast of the US is in the areas surrounding Chesapeake Bay. Delaware seems to take the brunt of the hit. I was surprised that there are parts of North Carolina that are so low-lying. The impact up and down the shore north of the Washington, D.C. area does not seem to be quite as dramatic.

Europe and The Middle East
Europe

The low countries in the northwest of Europe are the most obviously affected by a potential rise in sea-level. There are also parts of Italy and Ukraine that seem to be very low-lying. There are some minor impacts on Great Britain also. The middle east seems to be almost totally unscathed.

Australia
Australia

The effects are mostly on large parts of Indonesia and the northern coast of Australia. New Guinea is the most severely affected land-mass.

Asia
Asia

There are some minor effects along the eastern coastlines of both China and India. Bangladesh will certainly be severely affected. In addition, the southern tip of Vietnam seems to be potentially at great risk. The border between India and Pakistan may become submerged at the southern extremity. This may not be very bad given the current cozy relationship between the two countries! There are also some effects along the arctic shore of the continent just like for North America.

Africa
Africa

Africa takes the cake for being least affected by any potential sea-level increase. Except for some very minor areas around the eastern and western coasts near the center of the continent, the entire continent virtually unaffected by potential inundation from rising sea waters.

South America
South America

The major effects in South America are concentrated around the Amazon delta (could potentially make the Amazon a shorter river), and the northern coasts of Venezuela, Suriname, Guyana, etc. There are some effects along the at the Uruguay-Argentina border, the southern islands of Chile and the Falkland islands, but nothing that captures the attention like the inflow of oceanic water up the Amazon.

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