https://scholars.lib.ntu.edu.tw/handle/123456789/437705
標題: | Changes and threats of the taipei flood prevention system | 作者: | Shih, S.-S. Lai, J.-S. Hwang, G.-W. Shang-Shu Shih |
關鍵字: | Anthropogenic effects; Climate change; Floodway; Taipei flood Prevention; Tanshui River | 公開日期: | 2014 | 起(迄)頁: | 47-71 | 來源出版物: | Flooding: Risk Factors, Environmental Impacts and Management Strategies | 摘要: | Due to dense population living along the riverside, river flooding is one of the major hazards in Taiwan. The Taipei metropolitan area is the largest city with more than one-third of the total population of Taiwan. In this area, numerous severe flooding disasters caused by typhoon events have occurred and resulted in heavy losses. To mitigate flood-related disasters, a large-scale flood prevention program was implemented in 1963 and fully completed in 1999, namely the Taipei Flood Prevention System. The specific goal was to protect the Taipei metropolitan area against the 200-year recurrence flood in the Tanshui River. Levees and dykes of 32 km in length were constructed and improved along the river. Mitigation of floods for the Tanshui River system is inhibited by the bottleneck, which occurs at the smallest river width near the Taipei Bridge. Therefore, the Erchung Floodway was established to divert some of the flood water. The specific goal of the Erchung Floodway was to divert 9200 m3/sec peak flood discharge under a 200-year return period flood. However Erchung Floodway's function has been changed over time by urban development and natural alterations including river sand mining, riverine park construction, riverine plant succession, bridge construction and so on. Riverbed elevation changes due to sand mining are believed to have influenced the strength of the Taipei Flood Prevention System and thus were discussed in this study. The current protection criteria and impacts from anthropogenic effects and climate change threats were also examined. Both the physical and numerical models were used and analyzed. The sensitivity analysis of thirty-two scenarios corresponding to four factors has been investigated, including riverbed elevation, riverbed roughness, and water stage at the river mouth under the Q200 flood. The simulated results show that the flood diversion capacity of the Erchung Floodway, a key infrastructure for dividing floods in the Taipei Flood Prevention System, has decreased by 30%. We also found that the Taipei Flood Prevention System will encounter challenges if the riverbed roughness in the Erchung Floodway increases by over 50%, the riverbed roughness in the Tanshui River increases by over 25%, and the Q200 increases by over 13%. We conclude that the degrading process of the Taipei Flood Prevention System due to rapid urbanization and the corresponding strategies including river roughness and riverbed elevation control are meaningful lessons especially for developing countries. A comprehensive and effective evacuation program and monitoring system is also suggested. © 2014 by Nova Science Publishers, Inc. All rights reserved. |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/437705 |
顯示於: | 土木工程學系 |
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