Island Became Mainland

On July 11, 2013 · 9 Comments

Twelve Mile Circle is always up for a good challenge. Loyal reader Greg laid-down the gauntlet yesterday in the friendliest way possible of course, on Largest Artificial Islands: "A more common phenomenon, surely, must be islands joined to a mainland by landfill. So what about the opposite of this post, the largest former islands?" I became completely fixated, naturally. The original article I planned for this evening will just have to wait a couple of days while I focus my energy on this all-important question.

I established some ground rules. First, I assumed any landfill joining an island to the mainland would have to be man-made to keep it within the spirit of the previous article. Otherwise 12MC’s article on tombolos could be a nice starting point, or maybe I’d flag the ephemeral islands of the now dessicated Aral Sea. Second I assumed that "former island" meant that the original landmass still existed albeit as part of a larger landmass. If one took "largest former island" too literally, one might consider islands that had sunk below the surface of the sea.(¹) and I didn’t want to deal with that. Third, I discarded bridges, causeways and tunnels. The island had to be substantially integrated within surrounding terrain, not attached solely to it by a dirt trail, a ribbon of asphalt or a set of tracks. Otherwise I’d point to the Chunnel, make Great Britain part of Continental Europe and call it a day.

This challenge proved much more difficul than I imagined. I had trouble crafting effective search queries that eliminated false positives and faux connections, particularly those pesky bridges and causeways. I found that variations on "land reclamation" were the most powerful queries although they created so many results that it was difficult to separate legitimate island wheat from the greater preponderance of mainland chaff. Given that, one should not be surprised by examples I found in areas with significant land reclamation projects.

I also couldn’t determine a "largest" former island because sites tended to focus less on the before situation and more on the after. Whining aside, here was what I found:

The Netherlands

I discovered a wonderful before and after map of land reclamation in the Netherlands. The image didn’t have a Creative Commons license so you’ll need to open the link to view it if you’re curious. Flevopolder, mentioned in my previous article, is still an island so it shouldn’t be considered again. Nonetheless, notice that there were numerous islands in earlier days that became part of the mainland over the centuries.

Various Former Colonial Outposts in Asia

Jurong Island
Jurong Island by micamonkey, on Flickr
via Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic (CC BY-NC-SA 2.0) license

Singapore, Hong Kong and Macau all experienced significant land reclamation efforts. Some even focused on growing island sizes, islands joining other islands, and so forth. The reason was simple. They were highly confined territories bursting at the seams with people, so they had to grow up and out.

View Larger Map

Singapore’s Jurong Island served as a case study. It remains an island so that could be a drawback. However Jurong had a much more interesting backstory, "formed from the amalgamation of seven small islands into a world-class chemicals hub… home to more than 94 leading petroleum, petrochemical, specialty chemical and supporting companies."

That’s right it used to be seven island, all joined together: "From the 9.91 km² land area of the original seven islets, as of completion of the land reclamation on September 25, 2009 Jurong Island currently has a total land area of 30 km²."


China went overboard with island absorption during its recent economic boom to the point where it may need to take it down a notch, as reported in China Daily: "Connecting uninhabited islands to mainland by reclaiming land must be strictly restricted. The islands must be protected, and they should be prevented from disappearing, says … the [State Oceanic Administration of China’s] official website."

View Larger Map

I did some digging and found an example. Bingzhou Island became Bingzhou Peninsula connected to Xiamen’s Tong’an District on northwestern Dongzui Bay. Referencing a photo caption in Wikimedia Commons, reclamation continues to take place on the western side of Bingzhou in the proximity of the Tong’an Bridge. That was as of 25 February 2012 according to the caption. Apparently maps available online haven’t yet caught-up to geographic reality because Bingzhou continued to be represented as an island.

The United States

Coney Island at night
Coney Island at night by lusterbr, on Flickr
via Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) license

I had to find an example from the United States of course, and I discovered a good one. Coney Island, anyone?

View Larger Map

Doesn’t it seem odd that Coney Island is called Coney Island, even though it’s not an island? That’s because it used to be an island. Technically, I guess, it remains an island albeit part of the much larger landmass known as Long Island. Nonetheless Coney Island was once an actual standalone island and today it is not. The old name continues to be applied to its approximate original territory, an historic artifact of a previoius geographic configuration.

I don’t think I scored particularly well attempting to find the largest island attached to the mainland artificially, although maybe this was a start. People claim that Wikipedia has an article on everything. Apparently it does not. Maybe this exercise will serve as inspiration to one of 12MC’s several Wikipedians.

Thanks for the challenge, Greg!

(¹)SKIP THIS FOOTNOTE IF YOU’RE EASILY OFFENDED. It’s too bad I ignored sunken islands because I found one called Slut’s Bush near Cape Cod, Massachusetts. I thought this had to be a joke entry, however, the article provided links to a couple of much older sources including Cape Cod History. Now I’m almost afraid of the search engine hits I’ll have to endure.

On July 11, 2013 · 9 Comments

9 Responses to “Island Became Mainland”

  1. Greg says:

    Thorney Island, formerly in the Thames, is where Westminster Abbey was built as well as the original Palace of Westminster.,%20and%20the%20ancient%20course%20of%20Thames%20(%C2%A9%20MoLAS)

  2. Richard says:

    The map of the Netherlands that you linked is not a before-after map. It simply is a map that shows how much of the Netherlands is below sea level. For a real before-after map see:

  3. David Overton says:

    Another example might be the Isle of Thanet ( which was once separated from the rest of the English county of Kent by the Wantsum Channel ( The channel, which was once a major shipping route between London and continental Europe, gradually silted up over centuries, partially due to land reclamation by Augustinian monks in the 12th and 13th centuries.

    Despite not having been an island for nearly 500 years, the area of Kent has retained the name. We have some friends who live there and have visited it several times.

  4. CBE says:

    In regards to your footnote. Let’s not forget the wonderful seaside town of Gay Head, MA on Martha’s Vineyard. Sadly, they caved in 1998 and changed the name to Aquinnah.

  5. Pfly says:

    Two examples from Washington: Maury Island in Puget Sound, about 7 square miles, was connected to the larger Vashon Island. The connection is a narrow isthmus, but it had houses on it and isn’t just a causeway type of connection. Second, Seward Island in Lake Washington began Seward Peninsula when the Lake Washington Ship Canal was opened and the water level in the lake dropped significantly. Now it’s Seward Park, and about 300 acres.

    • Similar thing happened on a smaller scale just south of Seward Park: Pritchard Island. Where the water used to be is now Beer Sheva Park and Pritchard Island Beach. This explains why Island Dr. S. is on what is now the Seattle mainland.

  6. Pfly says:

    And a few more examples from the US (some might be borderline by your criteria): Bay Farm Island, CA (part of Alameda City); Coronado Island, San Diego, ~33 sq mi or so), Merritt Island, Florida (Kennedy Space Center), ~47 sq mi and now connected by more than just a causeway road I think; a number of things near DC you probably know about, like Daingerfield Island; League Island (Philadelphia); well, lots of possibilities near big cities built in low-lying areas, like NYC (maybe esp on the NJ side in the Bayonne and Newark areas), Miami, Bristol, Savannah, and so on. Boston obviously–East Boston was several islands once.

    I would think there must be some large examples in Europe dating way back, not just in the Netherlands area, but Denmark and the whole Baltic area, various delta-y areas, and so on. Don’t have more time to find a good example though. There’s probably river island examples too, where side-channels have been filled in…

  7. Joe Q says:

    There is some different way that this kind of things happen.

    1 Natural Erosion: It happens through the natural erosion of the earth.
    2 Natural Event: It could happen by a Volcan explosion
    3 Modern Architecture: Man had done several anexos to the seashore, In Panama City per example there is a place called La Cinta Coseta that is a an expansion of the seashore, and also the Articial Islands in Dubai.

    I have some pictures of La Cinta Costera in here >

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