Philippines

Protecting people and communities from the risk of floods in Metro Manila

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Residents were complacent when typhoon Vamco, locally called Ulysses, hit Kasiglahan Village in Montalban, Rizal, a province 29-kilomertes north of the capital Manila, on November 14, 2020. October and November 2020 brought a string of typhoons, including Goni (locally known as Rolly) -- the world's strongest typhoon in 2020--and didn't cause any visible damage to the community.

Little did residents know that these late-season storms, punctuated by Vamco, would cause the worst case of flooding in the village's history.

"The residents here weren't threatened by Ulysses because Rolly came and left without any damage," Vangie Serano, a resident and community social worker says. "We thought Ulysses would be the same. But we were wrong. The water from the river rose and before we knew it, the dike broke and flood waters, mud, and timber from the highlands inundated houses close to the river."

Around 8,000 housing units in Kasiglahan Village went underwater during Vamco's 24-hour siege last November. Eighteen homes were completely ruined, properties washed out, and residents forced to live in evacuation centers while waiting for flood waters to subside.

"The flood that day was strong and rose quickly," Vangie recalls. "Floodwaters rushed in fast, reaching the roof in seconds. There was no time to save anything."

For Vangie, Vamco brought the worst flooding incident that hit the village since she moved there more than two decades ago. Kasiglahan Village has been a known resettlement site for residents transferred from high-risk, flood-prone areas in Metro Manila. Ironically, she says, they were more at risk from floods in the resettlement village than in their previous homes in the capital.

Located at the foothills of the Sierra Madre mountain range, the village's flood is triggered by the river expanding to five times its size during an onslaught. It's also in the direct path of waters that roll downstream to inundate Metro Manila.

But if floods are high in Montalban, the waters are huge in the floodplains of Metro Manila and Laguna, a province south of the capital where the country's largest freshwater lake, Laguna de Bay, is located.

Perennial problem

Belen Arevalo, who has lived in Biñan, Laguna, a community surrounding Laguna de Bay, knew that during a typhoon, the lake water rises and engulfs her home. That was why her family saved up money from selling vegetables grown in their backyard to build up a two-story home where she lives with her husband and three granddaughters.

But when Vamco came, the waters easily flooded their home. "Our house has seven flights of stairs and (Vamco)'s flood reached the first five steps," Belen narrates.

She adds: "Our house goes underwater because Laguna de Bay overflows. When there's a typhoon, we usually move to my daughter's house that's further up because it's on higher ground and it also has a second floor."

When Vamco hit, Belen rushed to the highway in search of a safer place where they could relocate. "I ran to the highway and went searching for a safer place because the flood already reached the second floor of my daughter's house," she says.

Belen's family found refuge in an evacuation center, an unoccupied public school several kilometers away from the lake, where they stayed until the flood subsided. "It was really bad (staying at the evacuation center) with the COVID-19 pandemic," she said.

The flooding that Vangie and Belen deal with are emblematic of a bigger problem in Metro Manila and its nearby provinces, where flooding is a common occurrence.

Water from the Sierra Madre mountain range in the north rushes downstream through the Montalban River and reaches the flood plains of Marikina City, part of Metro Manila. From Marikina, water sweeps through the capital through the two main rivers, the Pasig and the Marikina.

The waters from Pasig are joined by water flowing out of Laguna Lake in its southeast border and flows out of the historic Manila Bay. Laguna de Bay, meanwhile, receives its water source from the provinces of Cavite and Batangas, making it a catch basin like Manila Bay.

The city's riverine system that cuts across Metro Manila has been likened to the Thames in London and to the Seine in Paris. But it also makes the Philippine capital susceptible to river runoffs -- and perennial flooding.

The city's most flood-prone areas are the coastal lowlands along Manila Bay, the Marikina flood plain, the communities surrounding the Laguna Lake plain, and the lowland areas along the Pasig and San Juan rivers.

Like Ondoy and Pepeng

For both Belen and Vangie, typhoon Vamco was reminiscent of similar calamities in 2009. That year was when Tropical Storm Ketsana, known locally as Ondoy, and Typhoon Pepeng (Parma) tore through the Philippines.

In quick succession, Ondoy and Pepeng came and dumped large amounts of rain causing widespread flooding in Metro Manila as well as central and northern Luzon, leaving close to a thousand dead and more than 700 injured due to drowning and landslides.

Flooding was particularly severe across the wide flood plains along the Upper Marikina River, low-lying areas along the Pasig, Malabon-Tullahan, Parañaque-Las Piñas, and Meycauayan Rivers, as well as the coastal areas and the shores of Laguna Lake.

Ketsana and Parma particularly caused extensive flooding in the Metro Manila area and the neighboring Rizal province, severely disrupting lives of over 9.3 million people out of an estimated population of 43.2 million living in the affected regions.

The storms had adverse effects across the economy, particularly in the enterprise, agriculture, and housing sectors. The private sector -- businesses, communities, and families -- has borne most of the impact of the disasters, which damaged properties; destroyed inventories, raw materials and machinery; and interrupted business operations.

A Post-Disaster Needs Assessment (PDNA) conducted immediately after the storms by the World Bank in collaboration with the Philippine government and development partners estimated that the storms caused a total damage and losses equivalent to about 2.7 percent of GDP. The regions hit by the disaster accounted for 60 percent of the country's GDP.

While Ketsana-level typhoons are expected to hit the Philippines every 10 years, the country's weather station anticipates the arrival of fewer but stronger typhoons due to erratic weather patterns.

Indeed, Ketsana and Parma would not be isolated cases. Vamco's visit last year brought rain that was close to the deluge caused by these two calamities in 2009. More areas were flooded.

In Kasiglahan Village, the difference between Vamco and Ketsana were significant. "When Ondoy (and Peping) came, only 4,000 homes in Kasiglahan Village were flooded," Vangie says. "But Vamco inundated 8,000 out of the 14,000 homes here--that's how big Vamco's flood coverage is; its double than Ondoy and more residents lost their homes and properties."

Studies show that floods that occur every 2 to 10 years could easily cover these lowland areas--more so floods that come every 50 to 100 years, according to the February 2011 Natural Disaster Research Report of the National Research Institute for Earth Science and Disaster Prevention.

Manila Bay's sea level has been rising four times faster than the rest of the world. The city's land is anticipated to sink by two meters by 2060 or by 4 to 6 centimeters per year due to ground subsidence caused by groundwater extraction.

With rapid population and economic growth, the capital's water demand is anticipated to increase. As illegal groundwater extraction and infrastructure developments continue, land subsidence is expected to escalate. With the onslaught of late-season typhoons like Ketsana, Vamco and Goni, Metro Manila and its nearby provinces becomes even more susceptible to severe flooding.

Metro Manila Flood Master Plan

In response to the PDNA recommendations after Ondoy and Pepeng in 2009, the Government, supported by the World Bank, prepared the Metro Manila Flood Management Master Plan.

For implementation over a 25-year period, the Master Plan provides a blueprint or roadmap for addressing the problems of floods in Metro Manila and surrounding areas.

It contains a thorough flood risk assessment, outlines a comprehensive flood risk management plan, and proposes a set of priority structural and non-structural measures to lessen the vulnerability and strengthen the resilience of the Metro Manila and surrounding areas against destructive floods.

Structural or engineering solutions include flood management dams, river improvements, floodways, among others, while non-structural mitigation measures include land use regulations, watershed conservation, reforestation, among others, and preparedness measures including improving the flood warning systems, rainfall and water level gauging stations, and information systems.

Specifically, the master plan proposed a set of measures to effectively manage major flood events, which include the following:

  • Reduce flooding from river systems that run through the metropolis, by building a dam in the upper Marikina River catchment area in order to reduce peak river flows entering Metro Manila during typhoons and other extreme rainfall events;
  • Eliminate long-term flooding in the flood plain of Laguna de Bay, to protect the population living along the shore against high water levels in the lake;
  • Improve urban drainage, including modernization of Metro Manila's pumping stations; and
  • Improve flood forecasting, early warning systems, and community-based flood risk management.

On September 4, 2012, the National Economic and Development Authority (NEDA) Board approved the master plan.

In 2015, the World Bank obtained US$6 million grants from the Australia-World Bank Philippines Development Trust Fund and Policy and Human Resources Development Trust Fund of Japan, to finance studies and designs of other interventions for the next phase of implementation of the master plan.

Implementing the Master Plan

Implementation of the Metro Manila flood master plan is underway.

Improving Metro Manila's Urban Drainage. On September 28, 2017, the World Bank, in partnership with the Philippine government and the Asian Infrastructure Investment Bank (AIIB) approved the Metro Manila Flood Management Project to improve urban drainage in Metro Manila.

The project aims to modernize 36 flood management pumping stations, construct 20 more including supporting infrastructure along the critical water ways in the cities of Manila, Pasay, Taguig, Makati, Malabon, Mandaluyong, San Juan, Pasig, Valenzuela, Quezon City, and Caloocan. Many of Metro Manila's existing pumping stations were built in the 1970s and have become inefficient and underperforming.

Solid waste clogs waterways and the entries to pumping stations, affecting the operation and maintenance of the pumps. The project will improve management of solid waste within the barangays (villages) near the drainage systems served by the pumping stations. It will also support the government's resettlement of informal settlers that are located on the waterways.

The project costs US$500 million, of which US$207.6 million comes from the World Bank, US$207.6 million from AIIB, and the remaining US$84.79 million is funded by the Philippine government.

The Department of Public Works and Highways (DPWH) and the Metro Manila Development Authority (MMDA) are implementing the project in close coordination with local governments and key shelter agencies. The project is scheduled to be completed by the end of 2024.

Improving flood management in the Pasig-Marikina River Basin. Flood management infrastructure is needed to temporarily store flood waters so that the remaining flood waters can be conveyed into Laguna de Bay and Manila Bay without causing flooding of urban areas. A project toward this end is under preparation, comprising a large Marikina flood management dam and a retention basin between the Montalban and San Mateo Bridges, both identified in the Master Plan as priority structures.

The proposed Marikina Multi-Purpose Dam is a 89 meter-high concrete gravity dam with a 384 meter long crest to be constructed across a gorge of the Marikina River to store floodwaters and reduce flood risks along Pasig-Marikina area. This will require the reservoir to be almost empty during the rainy season to capture floods.

The retention basin will have a 12 million cubic meter capacity necessary support to the Marikina dam. After a typhoon, water from both the Marikina Dam and the Rizal retention basin could be safely and gradually discharged to the Laguna Lake and Manila Bay.

There is a considerable land degradation of some areas in the watershed. Factors like erosion and climate change could result in higher water run-off and sediment loads getting into the dam. Measures including reforestation, rehabilitation of the catchment area, construction of sediment traps, and water quality monitoring could address these challenges.

The project would need the support of the small farmers and indigenous peoples living in the project area. There will be training and support to beneficiary communities and the implementation of community development and livelihood improvement projects related to agriculture, housing, and ecotourism selected with active participation of the beneficiary communities.

The estimated cost for the project is US$650 million. The dam is designed to reduce Marikina river discharge from 100-year rainfall events by 85 percent. The reservoir water has potential use for augmenting the city's water supply needs through a separate investment.

Managing Flood Around Laguna de Bay. Interventions to eliminate long-term flooding in the flood plain of Laguna de Bay to protect the population living along the shore against high water levels in the lake is yet to start. It is an important component of the Master Plan that needs to get traction for Metro Manila and its surrounding towns and cities to finally overcome the decades-old scourge brought about by the floods.

Back in Kasiglahan Village, Vangie says that after Vamco, their community is again discussing measures to curb flooding, a topic she hopes will end with a physical structure that will help their flooding woes. But what remains constant, she says, is that there is a growing need to solve their flooding problems.

"I hope we learn from this experience," Vangie says. "I hope there's a more concrete plan on how to solve this problem. Receiving relief goods are important, yes, but disaster management is more than that. There should be long-term plans because residents here are growing weary of the persistent flooding -- it's causing mental stress and division among us."