‘Landslide dams’ threaten Mindanao towns as quake aftermath alters river ecosystems

A hazardous geological phenomenon known as “artificial river damming” now threatens downstream communities in Mindanao after a massive magnitude 7.8 earthquake in Maasim, Sarangani last week destabilized mountain slopes, triggering massive landslides that have choked local river channels. This was revealed by the Office of Civil Defense (OCD) during a press conference on Monday, June 15, where updates on the aftermath of the powerful temblor that shook Mindanao last June 8 were provided by concerned government agencies. According to the Department of Environment and Natural Resources-Mines and Geosciences Bureau (DENR-MGB), the seismic shaking from the main shock in Maasim, Sarangani has left mountain slopes highly unstable, setting the stage for a secondary disaster as rain begins to fall. “The earthquake on June 8 caused instability in mountain slopes. Because the slopes are already unstable, when it rains, it can trigger larger landslides,” said DENR-MGB senior geologist Dr. Kevin Garas. He warned that the disaster is transitioning from earthquake-induced landslides into rain-induced landslides, creating high-risk blockages in local waterways. “The landslide debris went into the river and cut off the channels [of water]. That cutoff produced an artificial dam,” Garas explained. “When it rains, the water level can rise. If the dam breaches, it can cause flooding, flash floods, or even debris flow in adjacent municipalities along that river channel and downstream communities.” To prevent a catastrophic breach, the MGB and the Philippine Institute of Volcanology and Seismology (PHIVOLCS) are utilizing aerial surveys and ground assessments to locate these landslide dams and map out potential flash flood scenarios, ensuring that vulnerable communities are warned well in advance so they can evacuate. 736K individuals affected, 65 dead, 36 missing, thousands hurt The emerging environmental threat complicates an already massive humanitarian crisis as the OCD reported that the powerful earthquake has affected 176,186...