Abstract
Large rainfall-induced landslides are among the most dangerous natural hazards in Taiwan, posing a risk for people and infrastructure. Thus, better knowledge about the evolution of landslides and their impact on the downstream area is of high importance for disaster mitigation. The aim of this study is twofold: (1) to semi-automatically map the evolution of the Butangbunasi landslide in south-central Taiwan using satellite remote sensing data, and (2) to investigate the potential correlation between changes in landslide area and heavy rainfall during typhoon events. Landslide area, as well as temporary landslide-dammed lakes, were semi-automatically identified using object-based image analysis (OBIA), based on 20 Landsat images from 1984 to 2018. Hourly rainfall data from the Taiwan Central Weather Bureau (CWB) was complemented with rainfall data from Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) to examine the potential relationship between landslide area changes and rainfall as a triggering factor. The OBIA mapping results revealed that the most significant landslide extension happened after typhoon Morakot in 2009. We found a moderate positive relationship between the landslide area change and the duration of the heavy rainfall event, whereas daily precipitation, cumulative rainfall and mean intensity did not present strong significant correlations.
Highlights
The mountains of Taiwan, with the highest peaks rising to almost 4000 m a.s.l., are characterized by fractured rock formations, high relief and steep stream gradients
Our results indicate that the duration of the heavy rainfall event is the main parameter linked to the landslide area change, while cumulative rainfall and mean intensity did not show significant correlations with the extension of the Butangbunasi landslide
Landslides, theirfactors triggering factors and their potential to initiate cascading hazards is important in several respects
Summary
The mountains of Taiwan, with the highest peaks rising to almost 4000 m a.s.l., are characterized by fractured rock formations, high relief and steep stream gradients. These mountains, the central mountain range (CMR), influence the tracks and intensity of typhoon events [1]. Taiwan is regularly affected by typhoons (tropical cyclones), three to four per year on average, which bring heavy rainfall [2]. Some studies indicate that the number of typhoons hitting Taiwan increased after the year 2000, resulting in heavier precipitation in recent years [3,4].
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