Sinking cities

Without proper consultation and inclusive actions, the solutions to land subsidence may sink too


MANILA, Philippines – Land is sinking in the cities of Malabon, Kalookan and Navotas. Purple Romero reports.

UP geologists Fernando Siringan and Kevin Rodoifo said the land in Malabon and its neighboring cities Navotas and Kalookan has sunk by an average of 2.5 cms – 9.1 cms in 11 years since 1991.

Blame it on water pumping. When water is pumped from ground too much, the land could subside through the years.

In 2007, the government put in place a moratorium on extracting groundwater not just in these cities but in the entire Metro Manila. If water continues to be mined, people would get saltwater instead.

According to a 2004 Natural Water Resources Board paper, Metro Manila has a groundwater extraction rate of 2,548,700 cubic meters per day – which is equivalent to 1,000 swimming pools. 

Malabon residents experienced the effects of excessive groundwater extraction 20 years ago.

Tastes like the sea

48-year-old Rosalia Murillo says that they have been buying drinking water at P30 per drum since the water started tasting like the sea. That’s the other effect of water pumping.

Elenito Bagalihog of NWRB said they asked for the help of the Malabon local government unit in identifying illegal drillers – 14 of whom are allegedly in the city. The NWRB is undermanned, having only 14 tracking 22,000 permit holders.

The joint effort was not implemented, however, as factories questioned the legal basis of the monitoring.

Aside from stopping excessive extraction, though, the government also has to factor in land subsidence in designing flood control infrastructures – or else the project would not work, warn UP geologists.

DR. FERNANDO SIRINGAN, UP GEOLOGIST: Siguro [ang] mali namin sa approach ‘no is that we’re geologists and for us, kapag ang pagbabago bawat taon ay sentimetro, mabilis yun, kasi ang tinitignan lang namin ay thousands of years, even millions. Pero siyempre for a layman, for a non-geologist mabagal lang yun. Pero isipin mo, maski isang sentimetro kada taon, in 30 years time, 30 sentimetro. Puwedeng sabihin 30 sentimetro lang pala e, pero kung ikaw ay papasukin ng tubig baha na 30 sentimetro, ano na yun. Gawin mong dalawang sentimetro, kasi ang common ay 2-4 cms. per year. Yun yung range na nakita namin. At 2 cms. in 10 years time that’s 20. At 4 cms in 4 years time that’s 40.

This, Siringan said, is one of the major flaws of the polder dike,which was constructed in 2003 to protect northern Malabon from high tidal waves.

The polder dike is 12.6 meters tall, 8.1 km in width. It will take two hours to walk the whole stretch. In 2012, at the height of the monsoon rains, the polder dike was overtopped.

IMELDA SAYSON, RESIDENT: Mas grabe yung ito.
Rappler: hindi po naharangan?
Sayson: Wala yan tanggal yan.Harang, wala yan, lulutang lang yan.
Rappler: Hind naman po nasira yung bahay niniyo?
Sayson: Wasak yan, pinaayos lang namin yan.

This surprised local officials. 

REYNALDO CRUZ, DAMPALIT BRGY. CAPT.: Maraming epekto rito sa amin. Unang-una, lumaki tubig sa loob, nakarating sa baryo, nakarating sa kalsada, umahon sa mga bahay-bahay. E apektado, hindi lang naman kami apektado. Tumawid, nakarating sa Obando.

Fears of this happening was raised as early as 2004 by then Malabon Rep. Federico Sandoval. 

He said the resilience of the polder dike’s foundation was questionable. Its base is a bamboo grid – on top of it would be a layer of general textile material and sand.

Ripples and waves from the Manila Bay can weaken the sand layer.

Sandoval said that even if the polder remained intact, it would not be an effective barrier against tidal waves given the level of subsidence of 2.7 cms-9.1 cms per year, as measured by the UP geologists.

But Carla Bartolo, who manages the DPWH KAMANAVA flood control project, said the Japanese consultants who designed the polder dike took into consideration the problem of land subsidence.

CARLA BARTOLO, KAMANAVA FLOOD CONTROL PROJ. MANAGER: Kinonsider nila yan – kaya nga ang disenyo namin earth dike kasi nga subsidence. Tapos ang disenyo nila,itataas lang ng itataas, dadagdagan lang ng dadagdagan, yun ang disenyo nila precisely because of subsidence. Pero yung mga structures na naka-pilote, yung mga naka-compiles like pumping station, e wala, wala silang ano kasi naka-pilote naman yun.

Siringan said the measurements were wrong.

Don’t alarm them

But Bartolo said the geologists’ measurements were exaggerated.

In 2003, then DPWH Secretary Bayani Fernando already told Siringan and Rodolfo that they should not alarm the people with their concerns on the polder dike by directly going to the media instead of the DPWH.

Fernando said the scenarios geologists warned about did not always happen. 

In 2006, however, then DPWH Secretary Hermogenes Ebdane ordered the project design re-assessed.

DPWH engineer Gil Reyes submitted a report, which was never made public. He said though that corrective measures could be made after the project was done.

Bartolo said the polder dike has been completed – but local officials dispute that. Now they are wondering if it will ever be completed at all.

REYNALDO CRUZ, DAMPALIT BRGY. CAPT.: E sinasabi ni Sekretarya Carla Bartolo, fully completed daw, pero kaya nga ang sinasabi namin bilang punong barangay hindi nga kami maniniwala na yan ay tapos na dahil kasi kami ang nandun sa baryo e, kami nakakakita, kami nakakaalam. Hindi maniniwala mga ka-baryo ko na yan ay tapos na dahil nung nakaraang bagyo nakita nila pag-apaw ng tubig.

The polder dike – which is 12.6 meters tall – will be raised by another meter following the Habagat tragedy. The government also has to be more aggressive in preventing excessive groundwater extraction. These are supposed to address the twin problems of Malabon’s flooding and sinking land. Without proper consultation and inclusive actions, however, the solutions may sink too.

Purple Romero, Rappler. –