Monday, January 05, 2009

Ancient Land Reclamation in Manila Bay?

Check out these images from Google maps ( Click on the images to enlarge them.

The first is a satellite photo image of the northern Manila Bay:

Click image to enlarge

Now here is the same area but using a terrain rather than a photographic image:

Click image to enlarge

Notice the lakes in the image above that are missing in the first image, and also that the Pampanga Bay in the northwest corner extends much further northward than in the photographic image.

These are areas of reclaimed land that still show up in multi-spectral imagery because what is known as the spectral reflectance value is different than the surrounding land. When the lakes and bay were filled they retain a higher moisture content deeper than in the surrounding areas. So to imaging satellites, these still appear to be bodies of water.

So far, I have not been able to find any information on modern land reclamation projects in this region. There have been some further south in Metro Manila where the Cultural Center of the Philippines, for example, stands on reclaimed land. Most land reclamation projects involve modern construction, while the reclaimed land here is covered with old-style dike-pond (pampang) structures.

Since waterways are generally public, I doubt that these projects could have been completed without permission. The Pampanga Bay, for example, in the following overlay of the two images above is about twice as large in the terrain image.

Click image to enlarge

Indeed some old maps agree with the photographic image.

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(From: The Philippine journal of science. [Vol. 3, no. B], 1908)

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(From: Hannaford, Ebenezer, History and description of our Philippine wonderland, and photographic panorama of Hawaii, Cuba, Porto Rico, Samoa, Guam, and Wake island, with entertaining accounts of their peoples and modes of living, customs, industries, climate and present conditions, The Crowell & Kirkpatrick Co., 1899.)

So it appears that these bodies of water were not filled in in modern times, although this still needs some research I admit.

If they were filled in ancient times, the question is to whether it was an artificial process or whether it was due to natural siltation or possibly caused by volcanic lahar deposits.

Either way these areas can be useful in dating the building of this irrigation system. Since sediment would mostly have been used to fill these bodies of water in both the artificial and natural process, the organic material in the sediment can be carbon-dated. If there is evidence of dikes existing at one time on the former water's edge, it would mean that dike-building predated the land reclamation. It can also be said that at least the dikes and ponds built over these former estuarine bodies were not built before the land was reclaimed.

Paul Kekai Manansala