Development of a Citywide Real-time Landslide Warning System in Busan, Korea

Abstract

Rainfall-induced landslides have been one of major disasters in Korea where 70% of territory is covered by mountainous regions. As magnitude and frequency of extreme rainfall events has increased due to the global climate change, the number of landslide has significantly enlarged that results in casualties and property damages. In order to mitigate the landslide risk and to provide with an effective tool for public officials to manage the landside disasters, a citywide real-time landslide warning system has been developed by taking into account for situations in Busan, the second largest metropolitan city in Korea, as an application target area. The system provides with warning information based on five-alert levels that are classified as Normal, Attention, Watch, Alert, and Emergency. The warning level is determined by applying several thresholds developed by statistical, and physically-based as well as direct measurement-based approaches using forecasted/observed rainfall data or data obtained from a ground monitoring system. As a first step, the target area at ‘normal’ state is upgraded to an ‘attention’ state if the statistical thresholds are exceeded. Subsequently, the area delineated in the previous step can be updated to the next warning levels (watch and alert) by applying an infiltration-slope stability analysis when the safety factor of slope failure is less than 1.3 and 1.0, respectively. Finally, the ‘emergency’ state is determined by applying a debris-flow mobilization criterion and the subsequent potential debris-flow risk at specific local-scale areas are evaluated by conducting runout analyses. In order to validate the system applicability, landslide historical data and previous rainfall data during rainy seasons from 2009 to 2016 have been used. The system performance demonstrates a good agreement with the past landslide events. The developed system, therefore, will serve as a powerful tool to decision makers for landslide disaster preparedness.