## 5 Conclusions  
Large rainfall-induced landslides are among the most dangerous natural hazards in Taiwan, putting people and infrastructure at risk. Thus, better knowledge about the evolution of large landslides, their triggering factors and their potential to initiate cascading hazards is important in several respects.  
Figure 8: (**a**) Recently reconstructed road next to Butangbunasi. The photograph was taken on 8 April 2014. (**b**) Road construction and maintenance work at Butangbunasi. The photograph was taken on 28 June 2011. (**c**) Excavation work at the lower part of the Butangbunasi debris fan in the Laonong river bed. The photograph was taken on 15 November 2018.  
Often insufficient information exists on landslide occurrence and reactivation intervals. Findings from the analysis of time series of satellite imagery, as provided for example by the Landsat missions, can provide useful information for supporting hazard mitigation and spatial planning. At the same time, the constantly increasing amount of satellite imagery at higher spatial and temporal resolutions implies the need for efficient and robust landslide (change) mapping methods. OBIA provides a suitable methodological framework for addressing these challenges. In this study, we semi-automatically mapped the evolution of the Butangbunasi landslide using Landsat time series data. The OBIA mapping results showed that the most significant landslide extension happened after typhoon Morakot in 2009. Freely available rainfall data were analyzed to find potential relationships between the reactivation and evolution of the landslide area and heavy rainfall during typhoon events. Our results indicate that the duration of the heavy rainfall event is the main parameter linked to the landslide area change, whereas daily precipitation, cumulative rainfall and mean intensity did not present strong significant correlations.  
While landslides and associated hazards are a significant problem under present-day climate regimes, it is likely that climate change will lead to more frequent and extreme landslide-triggering events such as typhoons and tropical storms in Taiwan. Consequently, even more landslides may occur in the future. With this in mind, the relevance of studies that investigate and analyze the evolution of large landslides with respect to triggering events becomes even more important. Respective results can serve as input for hazard and risk analysis and the implementation of prevention and mitigation measures.  
Conceptualization: [PERSON]; methodology: [PERSON] and L.A.; validation: [PERSON] and L.A.; formal analysis: [PERSON], L.A. and Z.D.; investigation: [PERSON], L.A., G.P., T.-T.T. and A.-L.A.; data curation: [PERSON], L.A. and Z.D.; writing--original draft preparation: [PERSON], L.A. and Z.D.; writing--review and editing: [PERSON], L.A., Z.D., G.P., T.-T.T. and A.-[PERSON]; visualization: [PERSON] and [PERSON]; supervision: [PERSON]; project administration: [PERSON] and [PERSON]; funding acquisition: [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This research has been supported by the Austrian Academy of Sciences (OAW) through the project RioCa (Detection and analysis of landslide-induced river course changes and lake formation).  
The authors would like to thank [PERSON] for supporting field visits and for providing background information and UAV imagery. The used field photographs were taken by [PERSON], [PERSON] and [PERSON].  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.