EXPLAINER: Flood control projects planned for 39 sites across NCR by 2026

In response to severe flooding across the country, Malacañang announced the 39 sites in the National Capital Region (NCR) eyed for flood mitigation projects.

According to the Palace’s announcement, the types of projects include bioretention areas and detention ponds, river floodplains, and inland wetlands. Several rivers are also being studied for river renaturation.

Following the heavy rains in August 2026, authorities recorded 201.8 millimeters of rainfall in NCR in just five hours.

This is nearly half of the rainfall recorded during Typhoon Ondoy in 2009, when 455 mm of rain fell in Metro Manila over 24 hours.

Historically, a large portion of NCR’s drainage system was completed over 50 years ago. Because Manila had a much smaller population at the time, small pipes and narrow waterways were sufficient back then.

As time goes by, however, population growth, urbanization, and climate change have altered the country's drainage needs.

NCR drainage system upgrade

According to structural engineer Juan Paolo Bersamina, the NCR's drainage problem must be solved holistically.

“To think that drainage should be solved holistically, dapat buo natin siyang sino-solve rather than patche-patche 'yung pagso-solve natin,” Bersamina said.

(To think that drainage should be solved holistically, we should solve it as a whole rather than taking a piecemeal approach.)

He noted that urbanization in Metro Manila presents a massive challenge, adding to the expenses needed to complete the projects.

“Due to urbanization, marami nang nakatayong buildings. Minsan, doon na sa edge nu'ng drainage line so it's really, minsan, iko-consider mo na 'yung cost o pagbubungkal, 'yung maapektuhang building near the drainage,” Bersamina said.

(Due to urbanization, many buildings have already been constructed. Sometimes, they are built right at the edge of the drainage line, so you really have to consider the cost of excavation and the structures that will be affected near the drainage.)

“So sometimes, ‘yun na, nagkakaroon na ng domino effect na mahirap na lalong i-solve because of the urbanization,” he added.

(So sometimes, a domino effect occurs that makes it even harder to solve because of urbanization.)

For example, in Quezon City, P27 billion is needed just to complete its single drainage master plan, according to the local government unit. This represents more than half of the city's annual budget of P40.5 billion.

In the recently proposed flood mitigation projects, what types of structures is the government planning to build?

Detention ponds

A detention pond is a facility where rainwater is temporarily stored to prevent it from rushing into low-lying areas.

“Ang kalupaan natin is mayroong mataas na lugar, may mababang lugar. '’Yung ulan na dumaloy mula sa mataas na lugar, bubulusok 'yan sa mababang lugar,” Bersamina said.

(Our land consists of high areas and low areas. Rain flowing from high elevation will rush down to low-lying areas.)

“The purpose of the detention basin is sasaluhin niya 'yung baha na 'yun so that mapipigilan niya na bumuhos 'yung baha na 'yun further downstream,” he added.

(The purpose of the detention basin is to intercept that floodwater so it does not pour further downstream.)

In a highly urbanized area, a detention pond is considered the best solution to flooding.

However, it is not simply a matter of digging up land, as the area's overall drainage layout must be carefully considered.

Bersamina explained that connecting disconnected or misaligned drainage lines from different locations into a single detention pond presents a major engineering challenge.

River floodplains

A river floodplain is a flat area of land adjacent to a river.

It acts like a sponge that absorbs water whenever the river overflows, preventing floodwaters from surging directly into low-lying communities.

In addition, floodplains help absorb excess nutrients like phosphorus and nitrogen, which negatively impact rivers. They also provide significant benefits to local wildlife.

Inland wetlands

Considered the “Kidneys of the Earth,” inland wetlands purify and filter trapped inland wastewater before it flows into the sea and other bodies of water.

They can absorb large volumes of rainwater, thereby reducing or mitigating floods, and can even help combat drought.

“Hinahayaan mo siyang basa at a certain time. It also serves as a storage of rainwater or flood bago siya dumaloy sa downstream portion ng pampang,” Bersamina explained.

(You allow it to stay wet at a certain time. It also serves as storage for rainwater or floodwater before it flows to downstream banks.)

River Renaturation

In river renaturation, an artificial or damaged waterway is restored to its natural form and function.

“So binabalik mo sa ilog 'yung dapat niyang lapad, and then 'yung dapat niyang characteristics. Let's say, it should have trees on the riverbanks, may mga damo, ibinabalik po natin 'yun. Kasi ‘yung paglalagay ng mga greenery, let’s say mga grass in the riverbanks, that also helps reduce flooding eh,” Bersamina explained.

(So you restore the river's original width and natural characteristics. For example, if it should have trees and grass along the riverbanks, we bring those back. Adding greenery, like grass on riverbanks, also helps reduce flooding.)

The government also plans to add green spaces and green corridors—areas planted with numerous trees and vegetation to preserve biodiversity.

Establishment and rehabilitation of mangrove forests were also included in Malacañang's list.

According to Bersamina, while the projects have good intentions in theory, executing the plan for a place like Metro Manila will be quite challenging.

“Expensive kasi nga po, mag-a-acquire ka ng land. 'Yung iba, tumatanggi kasi nga 'yung mga may-ari ng property are supposed to develop that. Talagang babalik tayo du'n sa konsepto ng land use plan, na dapat, magkasundo lahat ng mga city,” he noted.

(It is expensive because you have to acquire land. Others refuse because property owners are supposed to develop those sites. We really have to return to the concept of a comprehensive land use plan, where all cities must be in agreement.)

According to Malacañang, the sites chosen for the projects were identified by the Dutch engineering consultancy firm Haskoning.

The Palace said its preliminary study has been completed, and authorities are now focusing on detailed engineering plans, which are expected to be finalized before the end of August 2026.—LDF, GMA News