Iloilo City wants BGC’s underground flood tank

By Rjay Zuriaga Castor

ILOILO CITY – As heavier rainfall increasingly overwhelms Iloilo City’s drainage system, the city government is studying the construction of underground catchment basins beneath public plazas as part of a long-term flood mitigation strategy.

Mayor Raisa Treñas-Chu said the proposed facilities may adopt the concept of the underground stormwater detention tank beneath Burgos Circle in Bonifacio Global City in Taguig.

The Burgos Circle basin is 12 meters deep, roughly the height of a four-story building, and can hold up to 22,000 cubic meters of floodwater, according to GMA Integrated News. It is one of only two retarding basins in Metro Manila, and it has been credited with keeping surrounding roads passable during heavy rainfall.

“We are identifying areas that can serve as catchment basins where floodwater can be temporarily stored so that it will no longer inundate communities that are regularly flooded. One of our proposals is to utilize the space beneath our public plazas,” Treñas-Chu said Wednesday, Aug. 5.

The city has already applied a similar concept in the rehabilitation of La Paz Plaza, where a retention pond was built to collect and temporarily store rainwater.

The stored water is reused to irrigate plants within the plaza, showing how stormwater management can also support water conservation.

Treñas-Chu said rainfall driven by climate change has grown more frequent and more intense, overwhelming drainage systems that were designed around historical rainfall patterns.

“Before, rainfall was usually less than 50 millimeters. Now, we can experience as much as 200 millimeters in just an hour,” she said.

She said recurring flooding is not solely the result of inadequate drainage infrastructure but is also aggravated by changing weather patterns linked to climate change.

“It’s not simply an issue of our drainage system. Climate change has significantly increased rainfall intensity,” she said.

To address the problem, the city government is finalizing a comprehensive drainage master plan that will identify flood-prone areas, assess stormwater runoff, determine the drainage capacity needed to withstand future rainfall, and guide long-term infrastructure investments.

“We have to review our drainage systems and determine their capacities. Through the comprehensive drainage master plan, we want to make sure that we can future-proof the city,” Treñas-Chu said.

She said the City Disaster Risk Reduction and Management Office is completing the master plan before the city hires consultants to undertake a detailed engineering study.

The drainage master plan is expected to serve as a blueprint for future flood control projects as Iloilo City adapts to more intense weather events.

The planning gap is not new. The 2017 Iloilo City Comprehensive Drainage Plan estimated that PHP 6.2 billion was needed to fully complete the city’s flood mitigation program, while the city needs PHP 14 billion to complete Phase II of the Japan International Cooperation Agency plan and PHP 7.8 billion for the full implementation of the Iloilo City Comprehensive Flood Control Master Plan.

Funding remains the binding constraint. President Ferdinand Marcos Jr. removed allocations for 2026 flood control projects under the proposed national budget, a decision that Iloilo City Lone District Rep. Julienne Baronda said cost the city roughly PHP 500 million under the National Expenditure Program.

The proposal also follows a difficult monsoon season. Treñas-Chu earlier pointed to ongoing flood control projects as a major factor behind the widespread flooding that submerged several parts of the city in late July following heavy rains brought by the southwest monsoon, enhanced by Tropical Cyclone Kiyapo, known internationally as Noul.

City government data showed that the city has conducted 421 declogging operations since 2025 as part of its flood mitigation efforts.

Treñas-Chu also urged residents to report clogged drainage systems, saying the city plans to establish a dedicated hotline and response team to act immediately on declogging requests.

“If you have requests for declogging, please let us know. We plan to establish a dedicated hotline and team that will respond specifically to these concerns,” she said.