Localized Early Warning Systems for Compound Slope Disasters: Insights from Rainfall-induced landslides after major earthquake

In January 2024, a significant earthquake struck the Noto Peninsula, causing numerous landslides across the affected region. Subsequently, in September 2024, the area experienced a 100-year extreme rainfall event, which triggered further large-scale landslides. These phenomena are considered to be compound disasters resulting from multiple interrelated factors.

The strong seismic shaking during the major earthquake weakened the ground strength across a wide area, leaving unstable sediment from collapsed slopes accumulated on mid-mountain regions. Even in areas where immediate damage appeared minimal, the seismic event significantly heightened the potential risk of landslides in mountainous regions. Under such conditions, subsequent extreme rainfall poses a high likelihood of triggering large-scale landslides.

To mitigate damage, it is essential to monitor potentially hazardous areas in mountainous regions following an earthquake and assess the degree of downstream risk to communities. Effective risk communication is vital to ensure residents take appropriate evacuation measures during heavy rainfall.

This study proposes a localized Early Warning System (EWS) that considers watershed dynamics and evaluates its significance. Drawing from the 2016 Kumamoto Earthquake, where IoT-based sensors were employed in a localized EWS, the effectiveness and challenges of such systems are discussed.

Based on the above, this paper explores monitoring methodologies aimed at preparing for compound slope disasters caused by post-earthquake heavy rainfall, with a focus on fostering safe and resilient communities.