For a storm-prone Philippine city, flood control is about more than infrastructure

CAGAYAN DE ORO CITY, Philippines — Saturnino Zambrano once ran a flourishing backyard farm on the banks of the Cagayan de Oro River on Mindanao Island in the southern Philippines. 

On Dec. 17, 2011, his life’s work vanished in a single night.  Tropical Storm Washi, known locally as Sendong, unleashed heavy rainfall on the island, swelling the river and causing massive flash floods and landslides that cut a wide swath of devastation in the cities of Cagayan de Oro and Iligan.

While their grown children managed to evacuate ahead of landfall, Zambrano and his wife stayed behind at home and survived by clinging to the top of a tree. “I couldn’t leave because I had so many animals; I wanted to rescue them, but there was no time,” says Zambrano, now 78, tearing up as he speaks. “The water was already too high [and] my livelihood was washed away.” 

The storm left more than 1,260 people dead and caused 1.3 billion pesos ($30 million at the time) in damage to agriculture and property. 

To protect against a repeat of the 2011 disaster, the Philippine government launched an 8.5 billion peso ($144 million) project aimed at mitigating floods in the Cagayan de Oro River Basin. Work began in 2019 and was completed in 2023, with the construction of 12 kilometers (7.5 miles) of dikes, flood walls and drainage inlets. Experts say these structures can help build flood-resilient communities, but they also raise concerns about vegetation loss and potential damage to wildlife and aquatic ecosystems due to construction, urging the government to look beyond gray structures and explore green solutions.

Flood control measures compromise mangroves, threaten coastal resilience

The structures built as part of the project are designed to shield 614 hectares (1,517 acres) along the Cagayan de Oro River, home to 60,900 people and 21,700 structures, from inland floods. Residents tell Mongabay that when Typhoon Rai (local name Odette) hit in 2021, the project, though just half-done by then, kept them safe and prevented casualties.

“Without this project, I struggled to fall asleep during heavy rains because I was traumatized by Typhoon Sendong,” says Evelyn Compasan, 44, an informal settler living along the Balulang dike. “Now we’re happy because we feel safe; when floodwaters rise, we know we won’t be swept away.” 

“People [living in danger zones] benefited in terms of security,” Ennyl Cananea, conservation section chief for the city environment and natural resources office, tells Mongabay. “Plus, new relocation sites were established, and they were moved there.”

Cananea also says the new structures improved the recreational spaces available to residents.

However, these benefits have come with an environmental price tag, not just an economic one. Although the government says the project will “contribute to the sustainable and progressive growth and development of the region,” data suggest it falls short on some environmental sustainability measures. 

The project’s 2013 environmental impact assessment report predicted that 7.1 hectares (17.5 acres) of vegetation would be lost due to the project’s construction. However, an analysis by Mongabay shows a loss nearly four times as large, 26.13 hectares (65 acres), from January 2019 to December 2023, coinciding with the construction period. This amounts to a 40% reduction in tree cover within 100 meters (330 feet) of the new storm control structures. These losses, experts say, could ultimately undercut the effectiveness of the system.

One hotspot for vegetation loss is the Bonbon neighborhood, along Macalajar Bay, where trees were cleared to make way for a nearly mile-long dike evacuation road. Locals, speaking on condition of anonymity, tell Mongabay that the cleared area once contained naturally growing nipa palms that shielded them during 2011’s Tropical Storm Washi.

“The decline of nipa mangroves may diminish their capacity to buffer coastal communities during severe flooding and storm surges in the long run,” Mary Jean Salvaña, an environmental science professor at the University of Science and Technology of Southern Philippines, tells Mongabay.

Vulnerable residents stay due to lack of livelihood opportunities at relocation sites

Relocation was ordered for families living in riverside areas such as Macasandig, Consolacion and Carmen, where flood-control structures had been built. More than a year after the project’s inauguration, residents like the Zambranos have stayed. They rejected the offer of free housing in Macapaya village, 11 km (7 mi) away, and opted to stay in a makeshift house made from scrap metal.

“Given our age, that distance is quite far,” Lerma Zambrano, Saturnino’s 76-year-old wife, tells Mongabay.

Once on track to retire comfortably, the couple are now struggling financially after losing their home and livelihood to Tropical Storm Washi. “I’m just staying here because I have nothing else to rely on,” Saturnino says. Today, they sell instant coffee and snacks to joggers on Macasandig Boulevard.

Ongoing forest loss, failed reforestation undermine flood mitigation efforts

The Cagayan de Oro government is already looking beyond just gray infrastructure by implementing nature-based solutions, like its flagship Project Lunhaw in 2020.

Complementing the built infrastructure project, Lunhaw (meaning “verdant” in Visayan) adopts a “blue-green framework” focused on managing water through rainwater harvesting and impounding facilities, enhancing green urban spaces, and protecting upland forests and watersheds, among other measures.

Since 2020, the city environment office has collaborated with village volunteers to plant native trees like lambago (Hibiscus tiliaceus) and different bamboo and mangrove species along the riverbank down to the coast. 

Cananea, however, notes that only 20-30% of the planted mangroves survived, citing a lack of wave breakers. She adds that unchecked infrastructure development has also changed water currents and increased sediment deposits, smothering the mangroves.

Planted native trees also suffer from local cattle grazing, while well-meaning civic groups have planted invasive species like African tulips (Spathodea campanulata) without proper coordination with the city environment office, highlighting what Cananea says is the need for greater public awareness. 

“There are no guards in the area, which makes monitoring a challenge for us. We can’t do it every day because we have other responsibilities as well,” she says.

But as the city government ramps up urban regreening in Cagayan de Oro’s downstream, tree cover, especially in upstream areas, has continued to decline over the past decade. 

From 2014 to 2023, Global Forest Watch recorded  tree cover loss of 583 hectares (1,441 acres) within the city limits, or the equivalent of 817 football fields. Of this loss, 41 hectares (17 acres) were primary forests — “green infrastructure” that could potentially have mitigated flooding by absorbing rainfall and slowing runoff, reducing flood peaks, and delaying flood peak times that could devastate downstream communities. 

Across the wider Cagayan de Oro River Basin, which spans 138,000 hectares (341,000 acres) and straddles three municipalities in the mountainous Bukidnon province, deforestation due primarily to decades of intense illegal logging and persistent agricultural expansion has been recognized as a significant contributor to recurring floods. The issue gained public attention only after Tropical Storm Washi. 

Since then, reforestation efforts across the river basin have mainly targeted easily accessible areas, although experts say these are less effective for flood mitigation compared to high-slope barren areas that better reduce downstream flood risks. 

“So, if that’s the problem, the solution is to restore the watershed there,” Roel Ravanera, executive director of local NGO Xavier Science Foundation, tells Mongabay, citing upland areas such as Bukidnon’s Kitanglad and Kalatungan mountain ranges.

“I’m not saying that building walls or bridges is bad — those are all important too,” he says. “[But] if you don’t address the root of the problem, the same issues will persist. Who knows, if it rains heavily again, their walls might get washed away as well.” 

Editor’s note: This story was produced with the support of Internews’ Earth Journalism Network as part of the Media Action on Sustainable Infrastructure in the Philippines. Read the story methodology here.