Group seeks rehab of Davao watershed to stop flooding

DAVAO CITY — The environment group Interfacing Development Intervention for Sustainability (IDIS) is calling for the urgent rehabilitation and restoration of the Matina Pangi watershed here, following the flooding that displaced 617 families (more than 2,000 people) and rendered some roads and bridges impassable on Jan. 4.

Although the swelling of the Talomo and Matina rivers was caused by the heavy rains spawned by localized thunderstorms that prevailed over the Davao Region days ago, IDIS pointed out that several manmade factors, including quarrying and other activities in upstream, had lessened the ability of the waterways to retain water during heavy rains.

In a statement signed by Mark Peñalver, IDIS executive director, the group cited satellite imagery assessments of the Matina River upstream showing significant patches subjected to earthfill and limestone quarrying that had reduced forest and vegetation cover, which hastened soil erosion that led to increased sedimentation in the river.

“Forest and vegetation help stabilize the soil … This sedimentation decreases the river’s capacity to carry water, causing water levels to rise more rapidly and intensifying the flooding experienced downstream,” the group pointed out.

IDIS also cited the river’s lack of wetlands, which could absorb or slow water flow during excessive rainfall. This condition is made worse by settlements along riverbanks, especially in designated floodplains, increasing the risk of flooding.

“Initial analyses suggest that intense rainfall in the upstream watershed areas was a primary driver of the surge in water levels,” it said. “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.”

Landfill

IDIS raised concerns about the presence of the sanitary landfill in Barangay New Carmen, as overloading leachate dams in the facility pose serious environmental and public health risks.

IDIS urged the city government to formulate a watershed and drainage management plan for the Matina Pangi watershed, considered the city’s smallest watershed with a catchment area of 7,879 hectares.

It also called for the enactment of strict regulation of nonmetallic mining and quarrying activities in the area; strict enforcement of riverbank protection policies, including the construction of detention ponds and wetlands for flood water storage; and the rehabilitation of the sanitary landfill in New Carmen.

The flooding that hit the city on Jan. 4 affected the low-lying areas of Matina Pangi, Matina Crossing, and Matina Aplaya after the Talomo and Matina Rivers overflowed, rendering its main bridges impassable due to the depth of floodwater.

The recent flooding, however, did not claim lives. But IDIS recalled that the 2011 floods from the swollen Matina River left 10,000 homeless and 33 people dead, which was considered among the devastating calamities that hit the city.

“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,” IDIS said. “While the Jan. 4 flooding incident fortunately resulted in no casualties, it underscores the importance of acting swiftly to implement these protective measures.”