A landslide struck Banjarnegara, Central Java, on Sunday (Nov. 16). Based on geological data from Banjarnegara and Pemalang, the area is not located on an active fault. However, long-standing fractures have become the primary trigger of slope instability. As the rainy season begins, these fractures become saturated and increasingly prone to movement, leading to the disaster that claimed 11 lives, left 17 people missing, and damaged 182 houses.
“Areas prone to landslides are typically those with steep slopes composed of loose materials or fractured rocks,” said Professor Wahyu Wilopo of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada (FT UGM), on Wednesday (Nov. 26).
One of the key concerns following this event is the urgent need for an effective landslide early warning system.
Unlike tsunami or flood warning systems, landslide early warning systems are highly localized and require substantial funding as well as strong technical and human resource support for daily operation.
Professor Wilopo explained that the Indonesian National Standard (SNI) involves the installation of rainfall and slope deformation sensors, but many field systems fail to operate due to poor maintenance.
“The problem in the field is that many systems are poorly maintained due to limited and insufficient human resources to manage them,” he said.
In addition, relocating residents from high-risk zones is not easy, as it involves severing economic, social, and cultural ties to their place of origin.
Evacuation efforts are also often hindered by rugged terrain, weather conditions, limited accessibility, and the absence of standardized evacuation procedures that residents understand.
The situation is further exacerbated by “disaster tourism,” which causes traffic congestion and obstructs emergency personnel.
“Communities rarely or never participate in landslide evacuation drills, so they do not know what actions to take,” Professor Wilopo added.
In terms of typology, Professor Wilopo noted that fatal landslides usually begin with sliding or rotational movement, which then transforms into a rapid flow due to high soil saturation following heavy rainfall.
For this reason, communities must understand the early warning signs of landslides, such as ground cracks, leaning trees, subsidence, cloudy water at the base of slopes, or small soil slips.
“Larger landslides are usually preceded by vibrations and a rumbling sound,” he explained.
Preventive measures that communities can undertake include reducing slope gradients, building surface drainage, reinforcing slopes, and planting vegetation with deep root systems.
Professor Wilopo also reminded that houses should be built at a safe distance from slopes to reduce risks during a landslide event.
“Ideally, build houses at a distance twice the height of the slope, or place bedrooms in locations farthest from the slope,” he advised.
The government plays a vital role in long-term mitigation through the development of detailed landslide susceptibility maps, exposure assessments, and priority mapping for mitigation interventions.
In addition, early warning information from BMKG, the Geological Agency, and BNPB must be communicated swiftly and clearly to communities in high-risk areas.
“The government must strengthen early warning information and communicate temporary self-evacuation measures to safer locations,” he said.
Author: Alena Damaris
Editor: Triya Andriyani
Post-editor: Rajendra Arya
Photograph: BNPB