Is Camanava sinking?

Is Camanava (Caloocan, Malabon, Navotas and Valenzuela) really sinking into the sea? Or is the sea level merely rising?

Either way, Camanava’s local chief executives have sought immediate assistance of various national government agencies after geodetic experts linked the phenomenon to the problem of perennial flooding in that part of the metropolis.

The mayors, including the lone congressman who came to the Camanava Summit last Tuesday, Malabon-Navotas Rep. Ricky Sandoval, expressed apprehension after hearing, apparently for the first time, that Camanava could really be sinking.

Marine geologists from the University of the Philippines explained to officials during the summit the phenomenon of "ground subsidence" (sinking of land mass) blamed primarily on the combined effects of severe or excessive ground water extraction (use of artesian wells, locally known as poso) and the rising sea level due to the melting of the polar ice caps attributed to global warming. The experts said this "sinking" phenomenon could help explain the perennial flooding in the area.

"We don’t want the project to go to waste. If this is true, we don’t want the money to go to waste," Sandoval said, referring to the Camanava Flood Control Project. Luis Zosa, a project consultant, said however that the phenomenon was considered and its anticipated effects factored in in the design of the dikes.

Meanwhile, Caloocan City Mayor Enrico Echiverri asked engineers from the Department of Public Works and Highways (DPWH) why they are standing by the design of the flood control project they have no idea how fast Camanava is sinking.

"This revelation would be alarmist if not proven true. Please give us accurate information," said Echiverri.

Malabon Mayor Tito Oreta, an engineer by profession, said the concerned agencies should not trifle with this revelation.

Zosa earlier said that Metro Manila’s sinking rate is high but there was no record of groundwater extraction though he claims that a geomechanical study on Camanava has been made.

Experts from the UP National Institute of Geological Sciences (NIGS) earlier expressed concern regarding the Camanava flood control project because its design was reportedly based on old data. They said that recent studies on land subsidence could have been conveniently ignored.

Zosa said that some 20 years ago, Metro Manila, not only Camanava, was reported to be sinking at two centimeters annually. He said that in 2000, the rate of subsidence was nine centimeters.

"So, in 10 years, at the same rate, Metro Manila, including Camanava, would sink by about 90 centimerers (or three feet)," Sandoval said.

According to Zosa, this is a worldwide phenomenon. "There is nothing to be concerned about at the moment because there are engineering solutions," he said.

Meanwhile, Metropolitan Development Authority (MMDA) Chairman Bayani Fernando said yesterday that floodwaters continue to plague Camanava because DPWH engineers abandoned the 24 relief pumping stations (RPS) for one year.

Fernando said six of the RPS were ransacked by thieves and are now non-operational because of DPWH’s negligence in maintaining the stations. DPWH deserted their flood control system in 2001 after they turned over the program to the MMDA.

Fernando said that apparently there was miscommunication between the two agencies. But after last Tuesday’s summit, Fernando was more optimistic that they would be able to resolve the flood problem in Camanava.

Flood control czar MMDA Undersecretary Cesar Lacuna told summit participants that a P288-million rehabilitation fund for Camanava was included in the 2005 proposed budget. The rehabilitation include improving the drainage system, decloging and desilting major waterways and repair of 24 RPS. — With Evelyn Macairan