14:45 〜 15:00
[HDS05-15] Decades-long landform evolution and impact of the large-scale Silabaku landslide: A case study of Yusui stream in Taiwan
キーワード：Silabaku landslide, Deep-Seated Gravitational Slope Deformation, Rainfall-induced landslide, Landslide dam, Debris flow
On August 7, 2021, a devastating debris flow hit the Yusui stream in Taiwan, damaging the Minbaklu Bridge on the southern cross-island highway. The enormous quantity of debris flow was caused by a catastrophic rainfall-induced landslide at Mt. Silabaku, the source of the Yusui stream.
The main scarp of Silabaku landslide had been present for over 20 years, as identified in the historic satellite photo. The slope remained stable until typhoon Morakot struck southern Taiwan in 2009, resulting in 2486 mm of rainfall in 5 days. Over the following decade, several rainfall events further deteriorated the slope. The slope partially collapsed due to headward erosion along gullies, accompanied by spreading of the main scar and significant downward slipping of the residual slope.
This study integrates multi-temporal optical images to investigate the evolution of the Silabaku landslide and DTM data to calculate its volume. The pre-disaster LiDAR DEM reveals the deep-seated gravitational slope deformation (DSGSD) characteristics covering the entire slope surface. The slope experienced considerable displacement despite no erosion event being seen in the optical images.
After the large-scale Silabaku landslide, the DTM anomaly indicated a 60-meter subsidence in the source area and an estimated landslide volume over ten million cubic meters. The post-disaster UAV photos show evidence of a remaining landslide dam. The existence of the dam confirms that the Yusui stream was blocked, allowing water to accumulate and eventually bursting and destroying the Minbaklu Bridge in downstream.
The main scarp of Silabaku landslide had been present for over 20 years, as identified in the historic satellite photo. The slope remained stable until typhoon Morakot struck southern Taiwan in 2009, resulting in 2486 mm of rainfall in 5 days. Over the following decade, several rainfall events further deteriorated the slope. The slope partially collapsed due to headward erosion along gullies, accompanied by spreading of the main scar and significant downward slipping of the residual slope.
This study integrates multi-temporal optical images to investigate the evolution of the Silabaku landslide and DTM data to calculate its volume. The pre-disaster LiDAR DEM reveals the deep-seated gravitational slope deformation (DSGSD) characteristics covering the entire slope surface. The slope experienced considerable displacement despite no erosion event being seen in the optical images.
After the large-scale Silabaku landslide, the DTM anomaly indicated a 60-meter subsidence in the source area and an estimated landslide volume over ten million cubic meters. The post-disaster UAV photos show evidence of a remaining landslide dam. The existence of the dam confirms that the Yusui stream was blocked, allowing water to accumulate and eventually bursting and destroying the Minbaklu Bridge in downstream.