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Vol.49, No.4, PP.199-261
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1
Evaluating the Efficiency of Subsurface Drainage Systems during Large Landslides
49(4):199-213
Der-Guey Lin[1]* Kuo-Ching Chang[1] Eugene Choo[1] Miau-Bin Su[2]
* Corresponding Author. E-mail : dglin@dragon.nchu.edu.tw
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2
Evaluating the Efficiency of Stability Remediation Measures for the T16-Tower Pier Slope of the Taipei Maokong Tramway
49(4):214-232
Der-Guey Lin[1] Kuo-Ching Chang[1] Jui-Ching Chou[2]*
* Corresponding Author. E-mail : jccchou@nchu.edu.tw
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3
Feasibility Assessment of Heavy Rainfall Forecasting using Global Positioning System–Derived Zenith Total Delays
49(4):233-242
Tzu-Pang Tseng[1] Yu-Shen Hsiao[2]* Li-Chun Tseng[2]
* Corresponding Author. E-mail : yshsiao@nchu.edu.tw
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4
Establishing a Hillslope Failure Susceptibility Model Based on the Soil Water Index and Frequency Ratio Method
49(4):243-253
Yi-Jun Liu Su-Chin Chen*
* Corresponding Author. E-mail : scchen@nchu.edu.tw
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5
The Mobile Bed Flume Experiment of Single Woody Debris Initial Entrainment
49(4):254-261
Min-Chih Liang Su-Chin Chen*
* Corresponding Author. E-mail : scchen@nchu.edu.tw
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The Mobile Bed Flume Experiment of Single Woody Debris Initial Entrainment
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Min-Chih Liang Su-Chin Chen*

Abstract
This study conducted flume experiments that simulated the initial entrainment of single woody debris in a moving channel bed. Woody debris of different lengths, diameters and orientations to flow direction were used to explore their interactions with the moving channel bed. In addition, their mode of transport and variation of the flow
field were investigated. Results of test were compared to the initial entrainment of woody debris on a fixed channel
bed. For the sake of comparison, this study was divided into three parts. In the first part, laser scanning was used to compare channel topography before and after woody debris movement. The second part used particle tracking velocimetry(PTV) to establish the fields of surface flow and velocity. The final part assessed the stability of the woody debris stability factor. The results of these experiments indicate that woody debris orientation influences the flow field, flow velocity and the final bed topography. Topography changes influenced the mode of wood transport and their entrainment threshold. Woody debris oriented parallel to flow had two modes of transport; rotation and sliding to downstream.Under oblique and transverse placements, woody debris movement can also be divided into two; rotation and sliding two modes and rotation is majority. A notable difference between the fixed and the moving bed channel was that entrainment of woody debris was primarily initialized by buoyancy in the fixed bed, whereas both buoyancy and dragforce initiated movement in the moving bed channels. Finally, our results demonstrated that woody debris in a moving bed channel needed larger discharge to initiate movement than that in fixed bed channels.
Key words: woody debris, wood entrainment, mobile bed, flume experiment.
Department of Soil and Water Conservation, National Chung Hsing University, Taichung 402, Taiwan, R.O.C.
* Corresponding Author. E-mail : scchen@nchu.edu.tw
Received: 2018/10/16
Revised: 2018/10/30
Accepted: 2018/11/16
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Address:2FL, No.8, Lane 113, Xiamen St., Zhongzheng Dist., Taipei City 100, Taiwan (R.O.C.)