Volume 29 Issue 7 - September 4, 2015 PDF
Reflection of Typhoon Morakot – The Challenge of Compound Disaster Simulation
Yu-Shiu CHEN2, Yu-Shu KUO1, Wen-Chi LAI2, Yuan-Jung TSAI1, Shin-Ping LEE2, Kun-Ting  CHEN1Chjeng-Lun SHIEH1,2,*
1 Department of Hydraulic and Ocean Engineering, National Cheng-Kung University, Taiwan
2 Disaster Prevention Research Institute, National Cheng-Kung University, Tainan, Taiwan,
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Climate change has altered how disasters occur. In Taiwan, because of increasing intensity and frequency of extreme rainfall events. The compound disasters can combine small-scale floods, debris flows, shallow landslides, deep-seated landslides, and landslide lakes into a large-scale single disaster event. This commonly occurs when the accumulative rainfall (R) is smaller than 1000 mm with corresponding rainfall intensity (I) greater than 100 mm/hr. On the contrary, if there is a large accumulation of rainfall during a low-intensity rainfall event, deep-seated landslides or landslide lakes tend result. This occurs when the accumulative rainfall is greater than 1000 mm with corresponding rainfall intensity less than 100 m/hr.(Fig.1)

Typhoon Morakot had the largest recorded rainfall duration, lasting a total of 107 hours. Moreover, the maximum hourly rainfall reached 123 mm/hr and the accumulative rainfall reach 3000 mm at Alishan station during the Typhoon(Fig.2). The rainfall with the characteristics of a high-intensity, long duration, and wide range. It caused a compound disaster including five types of disasters in a short time: 56.5 ha of shallow landslide, two debris flow, flooding, deep-seated landslide, and landslide lake(Fig.3).

In the case of Hsiaolin Village, the compound disaster includes landslide, debris flow, deep-seated landslide, landslide dam formation, landslide dam break, and inundation. All of these disasters occurred around Hsiaolin village. In the past, a number of numerical models are developed for single-type disasters. These models focus on the analysis of disaster characteristics. However, in a compound disaster, every single component of these disasters is connected and interrelated. Therefore, a structure of linking simulation models is needed to provide a systematic analysis of compound disasters (Fig.3).

Fig.1 The relationship of rainfall intensity, accumulative rainfall and disaster types

Fig.2 Rainfall intensity and accumulative rainfall of Typhoon Morakot (Alishan precipitation station)

Fig.3 The locations of the disasters at  Hsiaolin Village

Fig.4 The model structure of compound disasters in Hsiaolin Village


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