CEBU has to venture on its next flood interventions not only on river-channel widening and drainage upgrades but with watershed rehabilitation such as reforestation and the establishment of buffer zones and retention basins, an expert said on Thursday, Nov. 27, 2025.
Hydrologist Danilo Jaque of Hydronet Consultants Inc. urged national and local government units (LGUs) to combine structural engineering works with nature-based interventions, saying Cebu’s recent flooding, from lowland to upland barangays, has revealed the limits of relying on concrete alone.
Jaque said structural fixes will keep falling short unless matched with upstream ecological restoration and interventions.
In an interview during the Water Secure PH Forum on Thursday, Jaque explained that flood control has long been dominated by “purely structural” approaches.
The forum, organized by the Department of Science and Technology 7 in partnership with Hydronet and the Asian Institute of Technology Thailand, was held to address these issues.
However, climate-driven extremes and rapid urbanization demand a shift toward hybrid and nature-based solutions, he said.
“Both approaches are effective when integrated,” he said. “We need structures, but we also need to preserve the ecology. Replacing everything with concrete is no longer sustainable.”
He cited lagoon systems and retention basins as key examples, allowing excess storm water to be temporarily stored, preserving natural hydrology at a time when rapid development means heavier runoff.
In the forum, he highlighted that data from the state weather bureau covering 2000 to 2024 shows significant fluctuations, with periods of both extreme rainfall and drought.
These variations, coupled with dense urban development concentrated within four kilometers of the coast, leave key cities including Cebu City (1.06 million population), Mandaue City (430,000) and Talisay City (270,000) highly susceptible to flooding, particularly in low-lying areas less than 20 meters above sea level.
He urged LGUs to base new drainage and flood control designs and projects on updated rainfall data from the Philippine Atmospheric, Geophysical and Astronomical Services Administration.
Structural Interventions to address the flood risks include:
Impounding structures/reservoirs: To hold back excess water during heavy rainfall.
River/Channel Improvement: To increase the flow capacity of rivers.
Improved Drainage System: To efficiently collect and transport urban runoff.
Diking/pump gates: To protect low-lying areas and control water flow.
Watershed depletion
Jaque said the worsening runoff in Cebu’s catchments stems from depleted watersheds — an issue identified as early as the 2000 watershed management study for Metro Cebu. The study recommended reforestation, agroforestry controls and buffer zones.
This also includes promoting responsible farming on upland slopes.
On the downstream side, he said there is a need to reassess easements and compute updated river widths and channel capacities to withstand larger floods.
Jaque pointed out that the recent flood events, based on analysis, were “slightly more than a 100-year” rainfall episode, which was far beyond what most older drainage systems were designed for.
Jaque said that the cities of Cebu, Mandaue and Lapu-Lapu all have drainage master plans, but many proposals remain sparsely unimplemented or unreviewed.
“What’s necessary is reviewing and implementing them and updating these plans to reflect new rainfall data and changes in land use.”
Asked for examples of effective and ineffective projects, Jaque cited Mandaue’s Butuanon River flood control project, which was designed in two phases: low-level protection and a second phase for major flood events.
“As I was told, phase one is almost complete. It should work for smaller rainfall events — around the 10-year return period. But without phase two and without upstream management, even good structures can be overloaded.”
Pressed on how much government must allocate for impounding systems and basin improvements, Jaque said the Department of Public Works and Highways has costed several solutions in past studies.
Cost remains a major consideration, as he revealed that structural projects covering the cities of Cebu, Mandaue, Talisay and Lapu-Lapu are estimated at around P25 billion, emphasizing that this only covers engineered solutions.
Nature-based measures, such as watershed rehabilitation, catchment investigations and sustainable farming practices, require additional investment and integration.
With respect to the Cebu Provincial Government proposal to construct dams in Mananga, Butuanon and Cotcot rivers, Jaque said that they must serve as flood control and water supply.
“These require proper feasibility studies, social impact assessments and consideration of local fault lines to ensure safety,” said Jaque.
Meanwhile, Sabo dams, floated by the National Government, were designed to trap debris and sediment and were also noted as a potential supplementary measure to reduce river blockages.
The Water Secure PH Forum runs until Friday, Nov. 28, and gathers government agencies, researchers, LGUs and international partners to craft recommendations for assessing Cebu’s water security and developing localized responses to flooding and water scarcity. / EHP