Environmental group Interfacing Development Interventions for Sustainability (IDIS) called on the city government of Davao for the urgent rehabilitation and restoration of the Matina Pangi Watershed following the floodings in Matina after Matina River overflowed last week.
On Saturday evening, Matina Pangi and Calinan District experienced heavy flooding due to heavy downpour in the hinterland of Davao City brought about by the shear line wherein Balusong Bridge along MacArthur Highway was temporarily closed to traffic after the river overflowed.
IDIS believed that the flooding highlights a combination of natural and human-induced factors, particularly in Matina Pangi Watershed, Davao City’s smallest watershed with a catchment area of 7,879 hectares.
In a statement, IDIS said that based on its satellite imagery assessments of the upstream areas of the Matina River revealed that significant patches of non-metallic quarrying (earth-fill or limestone) and other human activities may have significantly reduced forest and vegetation cover.
“Forests help stabilize soil and prevent erosion, particularly during heavy rain. The lack of sufficient vegetation accelerates soil erosion, leading to increased sedimentation in 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 said.
IDIS added that there is a lack of wetlands along the midstream and downstream sections of the Matina River.
“Wetlands act 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.
IDIS also cited the residential settlements along the riverbank as contributing factors to the flooding. The group said these settlements were placed at designated floodplains, which naturally retain water during high river levels.
“The encroachment into these floodplains increases the risk of flooding the settlements during peak river flow periods,” it said.
The group said one important consideration along the Matina Pangi Watershed is the presence of the Davao City Sanitary Landfill in Barangay New Carmen.
It said that overloading leachate dams in sanitary landfills also poses serious environmental and public health risks, particularly by increasing the volume of floodwater and pollution.
Leachate is a toxic liquid formed from rainwater and waste, that can contaminate the surrounding areas if not properly managed.
To address these recurring issues, IDIS emphasized the need for immediate and long-term measures incorporating nature-based solutions in infrastructural mitigation, Disaster Risk Reduction (DRR) policies, and public awareness for Matina Pangi Watershed.
The group cited measures that include the development of a Watershed & Drainage Management Plan for the Matina Pangi Watershed by the Local Government Unit (LGU); strict regulation for non-metallic mining and quarry activities; strict enforcement of riverbank protection policies; and construction of detention ponds and wetlands for flood water storage.
The group also cited the establishment of flood control and mitigation, such as pumping stations and flood gates at downstream settlements; increase forest cover and reforestation projects at midstream to upstream areas of Matina Pangi Watershed; rehabilitation of the Sanitary Landfill in Brgy. New Carmen; impose disaster vulnerability transparency of real estate and housing developments along the Matina River; and increase public awareness of climate and disaster risk hazards and zoning policies to help mitigate destruction of the watershed.
