The Land is Sinking: Building on Aqueous Foundation

Blogger's Note: High population growth, concentrated development and greedy land developers have combined to produce this sinking problem. Former fishponds converted to land is not a place to build your homes. Ask people in Malabon how they feel living in the stinking Venice of Metro Manila and you'll know what I mean.

This story was taken from www.inq7.net
http://news.inq7.net/regions/index.php?index=1&story_id=42466

Gov't scored for the rapid sinking of M Manila, C. Luzon
First posted 10:52pm (Mla time) July 05, 2005 By Tonette Orejas, Inquirer News Service

THE GOVERNMENT has yet to stop the excessive use of groundwater, the main cause of the rapid sinking of coastal plains of four Metro Manila cities and three Central Luzon provinces, said geologists.

Dr. Kelvin Rodolfo and Dr. Fernando Siringan, both of the National Institute of Geological Sciences of the University of the Philippines, said they alerted local and national officials about the problem four years ago.

They said areas north of the Manila Bay-Caloocan, Malabon, Navotas and Valenzuela (Camanava) in Metro Manila and Pampanga, Bulacan and Bataan in Central Luzon-are sinking at rates more than 10 times faster than the rise of oceans.

Global warming causes oceans to rise at 2 millimeters yearly, while subsidence in the northern Manila Bay villages was occurring at rates of 1.7 to 8.3 centimeters yearly, they said.

Their eight-year research, which began in 1997, showed that the sinking has led to worsening floods and tidal incursions in coastal communities or deltas.

Rodolfo is also a professor emeritus of the department of earth and environmental sciences at the University of Illinois.

In the latest paper they wrote on the problem, Rodolfo and Siringan observed that officials were "reluctant to accept our findings... even though these have been independently verified by geodetic data collected by the government's own Department of Public Works and Highways."

The paper is titled "Public and governmental reluctance to recognize regional subsidence, a major anthropogenic cause for worsening floods around northern Manila Bay, Philippines."

Selective
The DPWH, Rodolfo and Siringan said, was "also very selective in how it applies the subsidence evidence, either minimizing its importance or ignoring it altogether."

In their assessment, government efforts "favor short-term political contingency over efficacy."
"Local politicians build wells to court votes. Wealthy and politically connected fishpond owners, in addition to hindering drainage by illegally encroaching on estuaries, are major users of groundwater and do not allow monitoring of their pumpage," they said.

The government also pursues "expensive but ineffective dredging and flood-control projects funded with foreign loans [that] are vulnerable to corruption."

Government engineers and foreign engineering consultants, on the other hand, "ignore, deny or
minimize the implications of their own geodetic confirmation of rapid subsidence."

The areas in which subsidence is taking place are wide, spanning 3,000 square kilometers.
Flat and very near the sea level, their supposed one-meter elevation extends 10 to 20 km inland. Southwest monsoon winds (habagat) and typhoons dump a maximum of 4,000 mm of rains from May to October. The winds raise tide levels, stopping floodwaters from draining to the bay.

While the Manila Bay delta areas have been naturally subsiding at rates similar to two deltas in Italy and the United States, the local situation has been hastened by the pumping out of groundwater, which causes the land surface to sink, Rodolfo and Siringan said.

"Every coastal metropolis in the world where groundwater has been withdrawn at rates greater than recharge, experiences serious subsidence," they said, citing the case of seven Asian cities that have dealt with serious floods related to sinking.

In the northern Manila Bay areas, groundwater is obtained for fishponds, plantations and recreational facilities, such as golf courses and swimming pools.

They cited the need for government assistance in measuring subsidence in illegally built fishponds, saying they were met there by private armies.

"In the meantime, we can only speculate that fishpond pumps may cause as much land subsidence as it does in the Yun-Lin area of Taiwan, where extensive fishponds use so much groundwater that they have caused the land to subside 0.66 m from 1989 to 1997. This equates to an average rate of 8.2 cm yearly, either coincidentally or significantly, virtually equal to the 8.3 cm yearly occurring at a fishpond area in Bulacan," they said.

Floodwaters rose by 0.2 meter in Bulacan and the Camanava area and 0.3 meter in Bataan and Pampanga from 1991 to 2002. Tide levels rose by as much as the same heights in those 11 years, and took a day to ebb.

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