DAVAO CITY (MindaNews / 8 Jan) – The environmental group Interfacing Development Interventions for Sustainability (IDIS) believes that the recent flooding incident over the weekend brought about by the localized thunderstorms was caused by a combination of “natural and human-induced factors.”
In a statement sent to MindaNews on Tuesday, IDIS stated that intense rainfall in the upstream watershed areas was a “primary driver of the surge in water levels” and could cause the river to overflow when combined with other factors such as “reduced capacity of the river due to sedimentation and the absence of wetlands.”
IDIS also noted that residential settlements along the riverbank exacerbated the flooding by “blocking natural drainage pathways,” leaving floodwaters with limited avenues to subside.
“These settlements were placed at designated floodplains, naturally retaining water during high river levels. The encroachment into these floodplains increases the risk of flooding the settlements during peak river flow periods,” it added.
According to the data released by the Office of the Civil Defense (OCD)-Davao last Monday, the localized thunderstorms flooded some parts of Barangays Matina Aplaya, Matina Crossing, and Matina Pangi and affected 617 families or 2,211 persons after Matina River overflowed.
IDIS stressed that satellite imagery assessments showed that non-metallic quarries of earth fill and limestones and other human activities might have reduced the forest and vegetation cover in the upstream of Matina River.
“Forests help stabilize soil and prevent erosion, particularly during heavy rains,” it stated. IDIS emphasized that the lack of sufficient vegetation can only accelerate soil erosion, bringing more sediments into the river.
“This sedimentation decreases the river’s capacity to carry water, causing water levels to rise more rapidly and intensifying the flooding experienced downstream,” it stressed.
The group emphasized the urgent rehabilitation and restoration of the Matina Pangi Watershed, the city’s smallest watershed with a catchment area of 7,879 hectares, which could potentially help control floods.
The environmental group noted the lack of wetlands along the midstream and downstream sections of Matina River, which could have helped mitigate floods by acting as “natural sponges, absorbing and slowing water flow during excessive rainfall.”
“The degradation or absence of these critical ecosystems limits the river’s ability to manage surges in water volume. As a result, heavy rain upstream leads to a more rapid and severe overflow in downstream areas like Matina, where there are no wetlands to help mitigate the impact,” it said.
To address the recurring flooding problem, IDIS said immediate and long-term measures are needed while taking into consideration the “nature-based solutions in infrastructural mitigation, Disaster Risk Reduction or DRR policies, and public awareness for Matina Pangi Watershed.”
Among the programs that IDIS has recommended to the local government of Davao include the development of a Watershed & Drainage Management Plan for the Matina Pangi Watershed; strict regulation for non-metallic mining and quarry activities; strict enforcement of riverbank protection policies; and integration of Sustainable Urban Drainage Systems or SUDS designs such as natural trenches, lagoons, stormwater parks, and permeable surfaces to public works and infrastructure development.
It also recommended construction of detention ponds and wetlands for flood water storage; establishment of flood control and mitigation, such as pumping stations and flood gates at downstream settlements; reclamation and improvement of riparian zones or legal easements through sustainable designs and riparian reforestation; and increase forest cover and reforestation projects at midstream to upstream areas of Matina Pangi Watershed.
IDIS stressed the importance of forming community-based environmental and disaster volunteers, imposing disaster vulnerability transparency in real estate and housing developments along the Matina River, and increasing public awareness of climate and disaster risk hazards and zoning policies. (Antonio L. Colina IV / MindaNews)
