Recent mudflows impacting parts of West Bandung were not typical landslides, but rather the result of a natural landslide dam collapsing upstream, according to a geologist from the Bandung Institute of Technology (ITB). The disaster, which struck Pasirkuning, Pasirkuda, and Sukadami hamlets on Saturday, January 24, involved a surge of mud, sand, and rocks delivered through river channels.
Understanding the Disaster
Imam Achmad Sadisun explained that houses were impacted by material originating upstream, rather than sliding from their original locations. The primary cause was a blockage on the southern slopes of Mount Burangrang, where landslide debris formed a dam across upstream river channels.
This blockage trapped water, which eventually became saturated and burst, releasing a powerful flow of debris downstream. Prolonged rainfall reduced the strength of the slopes, contributing to the initial slide and subsequent dam formation.
The Ongoing Threat
Sadisun warned that the risk of similar events remains. Expert teams have identified existing blockages in upstream sections of the river system. Should heavy rainfall return, these blockages could fail, sending further debris flows toward settlements.
Recognizing the Warning Signs
A key indicator of potential danger is a change in river flow. Residents are urged to closely monitor water levels, as a sudden decrease or disappearance of flow during heavy rain suggests upstream damming. In such cases, immediate evacuation from river channels is advised.
Sadisun suggests mitigation efforts should include debris-flow barriers and monitoring systems, such as geophones, in addition to reforestation.
What Could Happen Next
If rainfall increases, the existing upstream blockages could become unstable. This could lead to further dam failures and subsequent mudflows impacting downstream communities. Monitoring river flow and heeding warnings will be crucial for residents in affected areas. It is possible that authorities may need to implement evacuation procedures if the threat level rises.
Frequently Asked Questions
What caused the mudflows?
The mudflows were caused by the collapse of a natural landslide dam upstream, not by typical landslides, according to Imam Achmad Sadisun of ITB.
What areas were affected?
The disaster impacted Pasirkuning and Pasirkuda hamlets in Cisarua Subdistrict, and Sukadami hamlet in Lembang Subdistrict.
What should residents do if they notice a change in river flow?
Residents are urged to move away from river channels immediately if they observe a river that usually flows suddenly receding or disappearing during intense rain, as this signals upstream damming.
Considering the potential for recurring events, what steps can communities take to better prepare for similar disasters in the future?
