EXPLAINER: Why are the Sierra Madre and nature-based solutions important vs floods?

Rising up to 6,283 feet and with a length of 540 kilometers, the Sierra Madre Mountain Range serves as the backbone of Luzon Island and one of the most important land formations in the Philippines.

According to a report by GMA News Regional TV’s Jasmine Gabriel-Galban, the Sierra Madre has 40 percent of the country’s forest cover which serves as the primary defense of many provinces against seasonal typhoons.

But based on a study by the Haribon Foundation, the Sierra Madre loses 9,000 hectares of forest cover annually due to illegal logging and timber poaching, excessive mining, quarrying and kaingin (a traditional method of agriculture where farmers clear forest or woodland by cutting down and burning trees and vegetation to plant crops).

Add to these are developmental projects and the construction of structures on the mountain range itself.

From 2003 to 2020, a total of 130,000 hectares of forest cover has been lost in the Sierra Madre.

Experts have warned that if this continues, the Sierra Madre will gradually weaken in its capacity to act as Luzon’s protective wall and that the mountains that defend many areas would themselves trigger many calamities.

According to urban planner Paolo Alcazaren, a renowned architect, many communities in the Philippines are flood-prone since these are located downstream of rivers or in coastal lowlands.

Similar to a batya or washing basin, water will flow to the lowest point and settle in the middle.

“Majority of the 1,500 towns and cities in the Philippines are at the bottom of the slope from each of the islands. So there are uplands where the rain falls, ‘yung tubig baha will fall from that. But because we are deforested more than 90% of the original forest cover is gone. All of that water is going down to the 16 major river basins and river systems in the Philippines. And at the bottom of all of these are most of our towns and cities,” he said.

As an example, Metro Manila is situated on a low-lying floodplain that is bordered on two sides by the Manila Bay and Laguna de Bay that are both connected by the Pasig River. To the north of the Laguna de Bay is the Sierra Madre Mountain Range. During heavy rains, water flows from the Sierra Madre downwards via river systems connected to the Laguna de Bay. When the Laguna de Bay’s water level rises simultaneously with high tide in the Manila Bay, the accumulated water has nowhere else to go except to the roads of Metro Manila.

Alcazaren said no matter how many flood control projects are undertaken, if there are no solutions for the floods coming from upstream or higher elevations, the problem will just continue.

“Reliance on gray infrastructure is not the ultimate solution, which really needs to happen at the upper elevations. First for reforestation; second to detain the rain water before it gets down via dams, via detention ponds. To use bioengineering or nature-based solutions, the rivers and waterways that we have,” the architect said.

Nature-based solutions also include open parks and green spaces that will absorb the water that would help prevent floods but a hurdle to their implementation is a lack of sufficient laws.

“In other progressive cities around the world, their nature-based flood mitigation, and some modern management, is based on a network of parks and open spaces. Unfortunately, in our towns and cities, we have not built any major park, much less a park system in the last 50, 60, 70 years,” Alcazaren observed.

There is also a lack of coordination and cooperation between public officials.

“Stormwaters do not recognize political boundaries, yet we seek to address these problems. ‘Oh, I’m the mayor of this town or city and I will solve the problems of flooding within our city.’, [It] just doesn’t work that way,” he said.

“What is lacking is coordination and collaboration, and venues for such collaboration and cooperation are non-existent because of apparent lack of admission of accountability and responsibility across the board in all our institutions,” Alcazaren pointed out.

In August 2026, Malacanang announced the placing of nature-based flooding solutions in different parts of Metro Manila. Among these are the building of detention basins in areas of higher elevations, river floodplains and inland wetlands.

The Protected Area Management Board is also pushing for steps that would broaden the conservation and management of protected areas in the Sierra Madre.

In Congress, there is a proposal to create the Sierra Madre Mountain Range Authority and a 10-year ban on logging, mining and infrastructure projects and any type of development within the mountain range.

These measures aim to restore 50,000 hectares of protected land and to secure ancestral domains of the Dumagat-Remontado and Agta communities.

Experts have proposed many solutions to counter flooding and they say it is now the time for the government to listen to what they have to say in order to lift the country from the floods that are drowning Filipinos into an ordeal. —RF, GMA News