THE RECENT flooding in Davao City brought by the prevailing shear line that concentrated in the areas of Talomo and Baguio Districts affected the Talomo and Matina Rivers to overflow last Jan. 4, 2025. Main bridges along the Matina River were unpassable due to the depth of floodwater causing a flood crisis in residential settlements along Matina Pangi, Matina Crossing, and Matina Aplaya.
The Interfacing Development Interventions for Sustainability (IDIS) believes that the flooding incidence 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.
Based on our 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.
Additionally, 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.
Another significant contributing factor is the presence of residential settlements along the riverbank. 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.
Initial analyses suggest that intense rainfall in the upstream watershed areas was a primary driver of the surge in water levels. This surge, combined with the reduced capacity of the river due to sedimentation and the absence of wetlands, overwhelmed the system and caused the river to overflow. The urban settlements along the riverbank further exacerbated the situation by blocking natural drainage pathways, leaving floodwaters with limited avenues to recede.
One important consideration along the Matina Pangi Watershed is the presence of the Davao City Sanitary Landfill in Barangay New Carmen. Overloading leachate dams in sanitary landfills also poses serious environmental and public health risks, particularly by increasing the volume of floodwater and pollution. Leachate, the toxic liquid formed from rainwater and waste, can contaminate the surrounding areas if not properly managed. This issue often arises from underestimating leachate volumes or inadequate systems to handle excess leachate during heavy rainfall.
The Dec. 6, 2024 incident at the Davao City Sanitary Landfill in New Carmen highlights these dangers, as the leachate dam burst, releasing contaminated water that potentially worsened flooding and introduced hazardous pollutants into the environment. This spill threatened water quality and public health, leading to the evacuation of nearby families to protect them from toxic exposure.
To address these recurring issues, we need immediate and long-term measures incorporating nature-based solutions in infrastructural mitigation, Disaster Risk Reduction (DRR) policies, and public awareness for Matina Pangi Watershed.
- Development of a Watershed & Drainage Management Plan for the Matina Pangi Watershed by the Local Government Unit;
- Strict regulation for non-metallic mining and quarry activities;
- Strict enforcement of riverbank protection policies;
- Integrate Sustainable Urban Drainage Systems (SUDS) designs such as natural trenches, lagoons, stormwater parks, and permeable surfaces to public works and infrastructure development
- 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;
- Reclaim and improve riparian zones or legal easements through sustainable designs and riparian reforestation;
- Increase forest cover and reforestation projects at midstream to upstream areas of Matina Pangi Watershed;
- Rehabilitation of the Sanitary Landfill in Brgy. New Carmen;
- Formation of Community-based environmental and disaster volunteers;
- 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.
The Matina River flood in 2011 was described as the city’s most devastating disaster, leaving 10,000 people homeless and claiming the lives of 33 individuals. To prevent such a tragedy from happening again, it is crucial to enhance ridge-to-reef watershed protection and improve disaster management strategies for the Matina Pangi Watershed.
The recurring flooding incident serves as a reminder of the urgent need for an integrated watershed management plan that incorporates nature-based solutions and mitigates human-induced stressors on the Matina River. By prioritizing sustainable development practices and ecosystem restoration, the risks of future flooding can be minimized, protecting both the environment and the communities that depend on it. While the January 4 flooding incident fortunately resulted in no casualties, it underscores the importance of acting swiftly to implement these protective measures.
ATTY. MARK PEÑALVER
Executive Director
0939 630 7124
ENP. LEMUEL MANALO
Program Coordinator
0943 616 9092
JUSTIN JOSHUA PUNGYAN
Environmental Research Officer
0956 692 7319
