圖書典藏及影音數位平台

本計畫調查地點為淡水河，上游為大漢溪、新店溪及基隆河，大漢溪在江子翠會合新店溪後，成為淡水河主流。主流至關渡和基隆河匯流後，於淡水鎮油車口附近注入臺灣海峽。淡水河系分佈數個重要濕地，生物相豐富。另大漢溪上游石門水庫近年已完成電廠1 號鋼管排砂工程，也刻正辦理排洪減淤相關工程；因此本計畫將另針對石門水庫排洪減淤工程對生態及防洪等面向所遭遇的問題加以分析探討。

River regulation and management in Taiwan over-emphasized flood control and water resources demand before, but less considered the whole environmental ecology. In recent years, since environmental protection consciousness has been more and more important, there is a need to do more investigation to make up the shortage of existing material which should be integrated for the reference of public. To promote river business, river management, environmental conservation and rehabilitation, and provide the reference of natural treatment design for hydraulic engineering institute, all the basic material including Humanities, physiographic, hydrological data, biological, spatial utilization need to be collected in this project. The project is to investigate Tamsui River situations. The work target is to compile GIS ecosystem data as unit of river for the whole Tamsui Watershed and to build it into the database at the website for the Management Information System of River’s Investigation. Due to various natural and man-made causes, the bypass ability of the Earchung floodway has deteriorated since the completion of the flood control project for the greater Taipei, and this will compromise overall flood mitigation. Numerical modeling was adopted to identify factors affecting this ability. Suggestions are made and provided in this project as improvement measures. The 200y return period flood results in a flow discharge of 17,000cms for the Taipei Bridge section of the TamsuiRiver and a bypass flood discharge of 6,500 cms for the Earchung floodway at the current situation. The Taipei Bridge’s flood level, currently at 8.34m, is lower than the planned level of 8.40m. The sensitivity analysis result shows that riverbed roughness is the most sensitive (in negative correlation) of all internal factors of the Floodway, followed by the riverbed height (in negative correlation), and then the number of bridges (in negative correlation). For external factors, riverbed roughness of the TamsuiRiver is the most sensitive (in positive correlation), followed by riverbed height (in positive correlation), trash mountain removal (in negative correlation), and the water level at the river mouth (in positive correlation). The residents living along the TamsuiRiver are supposed to be protected avoiding a 200-yr return period flood inundation by the smooth operation of Taipei Flood Prevention System. However the reach between Guandu Bridge and TamsuiRiver mouth doesn’t meet the protection goal due to no high-level levee was built. Nine scenarios of different return period floods, such as 2-yr, 5-yr, 10-yr, 20-yr, 50-yr, 100-yr, 200-yr (2.30m), 200-yr (2.93m), 200-yr (4.03m), were simulated by the CCHE2D and were used to identify the potential inundation areas (PIAs). Seven areas, such as TamsuiOld Street, Sumeikern Creek, Guandu Temple, Waziwei Village, Neulioupu Creek, Wushantou Creek, Longshing Creek, were selected as the protection areas (PAs) by synthesizing the CCHE2D simulation results and protective areas including villages, industrial parks, heritages and so on. The main concern for mitigating the river flood impacts of the seven PAs is to present effective PIMs for evacuation. They are belonging to one of the non-structural strategies. The structural facilities are not recommended so far due to the uncertainty of land use limitation, landscape impacts, residents’ will of acceptance, and technical feasibility. We conclude the tackle timing of evacuation when the river level reaches the second flood warning stage and suggest the government authority to integrate the PIMs and flood warning stage proposed by this project as an early warning system for effective evacuation.

本報告為淡水河水系河川情勢調查的第二輪報告，旨在建置生態資源資料庫，並提出河川環境管理建議。計畫範圍涵蓋淡水河主流及三大支流，共設置15個樣站進行環境因子及生物調查。調查結果顯示，主流樣站多屬中度污染，支流部分樣站則為輕度或未受污染。棲地調查發現多樣化的水域型態與底質，並記錄了豐富的水域及陸域生物。通洪能力分析指出，部分河段存在溢堤或出水高度不足的問題，建議結合工程與非工程手段進行改善，並強調兼顧防洪與生態功能的平衡。此外，報告亦比較了歷次調查成果，顯示河川棲地已有改善趨勢。