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Water 2017, 9(2), 84; doi:10.3390/w9020084

Channel Planform Dynamics Monitoring and Channel Stability Assessment in Two Sediment-Rich Rivers in Taiwan

1
Department of Soil and Water Conservation, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung, 402, Taiwan
2
Center for Space and Remote Sensing Research, National Central University, 300 Jhongda Rd., Jhongli Dist., Taoyuan, 32001, Taiwan
3
Water Administration Division, Water Resources Agency, Ministry of Economic Affairs, 501,Sec. 2, Liming Rd., Nantun Dist., Taichung 408, Taiwan
*
Author to whom correspondence should be addressed.
Received: 30 November 2016 / Accepted: 25 January 2017 / Published: 30 January 2017
(This article belongs to the Special Issue Stream Channel Stability, Assessment, Modeling, and Mitigation)
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Abstract

Recurrent flood events induced by typhoons are powerful agents to modify channel morphology in Taiwan’s rivers. Frequent channel migrations reflect highly sensitive valley floors and increase the risk to infrastructure and residents along rivers. Therefore, monitoring channel planforms is essential for analyzing channel stability as well as improving river management. This study analyzed annual channel changes along two sediment-rich rivers, the Zhuoshui River and the Gaoping River, from 2008 to 2015 based on satellite images of FORMOSAT-2. Channel areas were digitized from mid-catchment to river mouth (~90 km). Channel stability for reaches was assessed through analyzing the changes of river indices including braid index, active channel width, and channel activity. In general, the valley width plays a key role in braided degree, active channel width, and channel activity. These indices increase as the valley width expands whereas the braid index decreases slightly close to the river mouth due to the change of river types. This downstream pattern in the Zhuoshui River was interrupted by hydraulic construction which resulted in limited changes downstream from the weir, due to the lack of water and sediment supply. A 200-year flood, Typhoon Morakot in 2009, induced significant changes in the two rivers. The highly active landscape in Taiwan results in very sensitive channels compared to other regions. An integrated Sensitivity Index was proposed for identifying unstable reaches, which could be a useful reference for river authorities when making priorities in river regulation strategy. This study shows that satellite image monitoring coupled with river indices analysis could be an effective tool to evaluate spatial and temporal changes in channel stability in highly dynamic river systems. View Full-Text
Keywords: channel stability; sensitivity index; satellite images; typhoons; braid index channel stability; sensitivity index; satellite images; typhoons; braid index
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Kuo, C.-W.; Chen, C.-F.; Chen, S.-C.; Yang, T.-C.; Chen, C.-W. Channel Planform Dynamics Monitoring and Channel Stability Assessment in Two Sediment-Rich Rivers in Taiwan. Water 2017, 9, 84.

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