Task force cites myriad of factors in city floods

By Rjay Zuriaga Castor

Iloilo City’s recurring flooding is largely due to poor inter-agency coordination, weak maintenance of waterways, informal settlements, and unregulated urban development that destroyed natural water channels, according to the city’s Drainage Task Force.

Engr. Mavi Gustilo, chairperson of the task force, said these findings were consolidated from consultations with various barangays, government agencies, stakeholders, and the task force’s monitoring initiatives.

During the 2nd quad committee hearing of the City Council, Gustilo said a key issue is the lack of collaboration between national agencies and the city government in collecting vital data.

She emphasized that accurate and complete information is critical in conceptualizing and designing effective flood mitigation structures.

She noted that the absence of data—such as existing waterways and invert elevations—has led to infrastructure projects that inadvertently worsen flooding.

“There are instances when a drainage system being constructed on a road ends up with a higher invert elevation than the existing barangay drainage, which blocks runoff and causes water to stagnate and clog,” Gustilo said.

She added that climate change and erratic weather patterns have further complicated planning and design efforts.

Although Iloilo’s monthly average rainfall is 120 millimeters, three successive storms in July dumped as much as 300 millimeters in just three days.

The task force also flagged the proliferation of informal settlers along river basins and tributaries as a major issue that disrupts water flow and delays infrastructure projects.

“It contributes to pollution and siltation, which obstruct the natural flow of water and constrict rivers, consequently reducing discharge capacity,” she said.

Gustilo stressed the need for inter-agency collaboration in clearing informal settlers before construction begins.

She also cited the poor maintenance of existing drainage systems, which often malfunction during heavy rains due to clogging.

Gustilo said urban development has further altered the natural flow of water, especially in areas where large-scale construction projects have been built near or over waterways.

She said these developments reduced the city’s water absorption capacity and called for regulations that ensure a portion of land remains unpaved to help absorb runoff.

Outdated flood mitigation structures, inadequate drainage, and unserviceable flood pumping stations were also flagged as critical issues.

Iloilo City has six pumping stations, but Gustilo said their operations are often delayed.

“Detention tanks are already full before they even get operational,” she said.

“We need to assess the operation and maintenance of our pumping stations, which are now under the local government.”

She added that some drainage outfalls are situated below sea level, leading to backflow during high tide.

Gustilo stressed that the city government must increase funding and focus on building and maintaining floodgates, while addressing siltation and the narrowing of waterways caused by both natural processes and unregulated development.