A University of the Philippines Cebu study presented to Cebu City officials identified narrowed river channels, upland runoff, and improper waste disposal as key factors contributing to city flooding.
The City Government is considering building detention ponds in upland areas to temporarily store rainwater and reduce runoff volume reaching low-lying communities during heavy rains.
City Hall is requesting an official copy of the study, including written explanations of data, to assess potential sites and determine priority flood mitigation measures.
NARROWED river channels, runoff from steep mountain slopes and improper waste disposal are among the factors contributing to flooding in Cebu City, according to a University of the Philippines (UP) Cebu study presented to City officials.
The City Government is considering detention ponds in selected upland areas and other flood mitigation measures based on the findings, said Kenneth Siasar, chief of staff of Cebu City Mayor Nestor Archival.
Siasar said the study examined areas where river channels have narrowed and how runoff from mountainous areas contributes to flooding in downstream communities.
One proposed intervention is the construction of detention ponds that would temporarily store rainwater and release it gradually, reducing the volume of runoff reaching low-lying areas during heavy rains.
Siasar said the researchers emphasized that large volumes of water flow from the mountains because of the steep terrain, putting pressure on waterways and drainage channels.
He said upland runoff remains a concern regardless of whether developments or detention ponds are present.
He explained that water from upland areas would continue to flow toward downstream communities, underscoring the need to manage runoff alongside other flood mitigation measures.
The study covered several waterways, including the Guadalupe, Butuanon, Kinalumsan and Mananga rivers. Siasar said the researchers also examined tributaries and smaller waterways in northern and southern areas, although the presentation focused particularly on flooding in southern communities.
Narrowed waterways
Aside from upland runoff, the study identified narrowing river channels as another concern, Siasar said.
He said some previously constructed flood control projects may have reduced the effective width of waterways because structures were built inward from riverbanks rather than outward.
Siasar explained that building structures inward may have been considered more practical because extending them outward could affect nearby houses and require the government to compensate property owners.
However, he said narrower river sections could limit the amount of water waterways can carry during heavy rainfall.
A detailed assessment of the affected locations and the extent of the narrowing would help the City determine which areas require intervention.
Improper waste disposal
The study also identified improper waste disposal as a contributing factor to flooding, Siasar said.
He described the problem as behavioral, noting that garbage can undermine the effectiveness of drainage and flood control infrastructure.
Siasar cited an incident in Barangay Tisa in which residents reportedly placed sacks of garbage on the road as floodwaters rushed through the area.
He said the incident illustrated how human actions could worsen flooding and complicate efforts to manage floodwaters during heavy rains.
The findings underscore the need for public cooperation, particularly proper waste disposal to prevent garbage from clogging waterways and drainage systems.
Siasar said flooding involves several factors, including rainfall, land development, the condition of rivers and drainage systems, and human behavior.
City to review findings
The City is seeking an official copy of the UP Cebu study, including written explanations of the graphs and other data presented by the researchers.
Siasar said the document would help officials identify suitable locations for detention ponds and determine which measures the local government could implement.
The City would also need to assess whether potential sites fall within areas it can develop or manage.
The findings are expected to help the City identify priority areas for flood mitigation and respond to a City Council resolution seeking an update on the research and the administration’s planned actions.
The construction of detention ponds remains a proposal under consideration, pending further review of the study and the suitability of potential sites. / CAV