圖書典藏及影音數位平台

為因應基隆河近年來保護標準下洪水量上升，防洪能力日益不足之問題，惟目前基隆河兩岸防洪牆皆已施做完成，其防洪工程不易再加高加強，加上兩岸社區亦已發展完成，宜辦理研究，謀求綜合治理措施來降低洪災風險，故為找出適應策略，辦理本計畫。

In recent, hydrologic studies in 2015 suggests 200-year recurrence flood discharge of the Keelung River as 6,600 cms without the consideration of diversion from Yuanshanzih, which is 45% increase comparing to the design flood 2,480 cms from previous regulation scheme. When considering Yuanshanzih diversion, the discharge of the Keelung River’s river mouth increases 1,660 cms from 3,690 cms to 5,350 cms, as well as 45% of original design level. The flood conveyance capacity now is much lower than expectation. However, current (flood embankment is not easy to be further enhanced because the floodplain is already a highly developing metropolitan area. Integrated flood management may be a solution for the Keelung River. This study suggests, for the increase of flood discharge in the Keelung River’s river mouth, 1,900 cms (77 %) is due to the increase of rainfall while the rest 580 cms (23%) is because of land development. In this study, one-dimension HEC-RAS model was used to analyze river discharge capability. The results revealed that the main flood risk area in the Keelung River are mainly from the SheZi Island river section (from river mouth to section 9 of Keelung River) and Xizhi river section(from section 50 to section 70 of Keelung River) and the 200-year flood caused 29 bridges have encountered insufficient freeboard which includes 8 bridges completed recently. The factors affecting flood control capacity of Keelung River are flood discharge of Keelung River, the flood discharge Tamsui River, the water level at the Tamsui River river mouth , mangroves, Manning’s n values, river siltation, bridge structures. According to the sensitivity analysis of each factor, the flood discharge of Keelung River is the most sensitive, followed by choked flow effect caused by the bridge. After simulating the demolition case of three old bridges such as SheHou Bridge, Jiangbei Bridge and Chang’an Bridge, the water level can be reduced by about 90cm. This study compares the flood control advantages of following cases: flood diversion scheme, tributary river closure scheme, floodway, tributary detention flood pool, tributary dam and underground detention river. Among these cases, the most effective flood reduction measure is either the Sijiaoting flood diversion scheme or the Sijiaoting flood diversion scheme with the left tributary diversion scheme. For the best, the maximum flood reduction effect of flood diversion scheme up to about 680cms and 860cms. In Sijiaoting flood diversion case, the reduced flood is almost equivalent with the discharge during Nari typhoon. The improvement program in the Keelung River is includes short-term 5-year and long-term 20-year plans. In short-term, the goal is to complete Taipei flood control construction in Taipei city section. Also for the upstream section of the Nanhu Bridge, conducting dredging and improving embankment will be conducted to prevent 200-year flood risk analyzed in 2015. The long-term goal is maintaining the status quo by retaining the existing embankment at Xizhi river section, and promoting the Sijiaoting diversion scheme to reduce the flood discharge to be equivalent with the discharge of Nari typhoon. In addition to the promotion of disaster prevention systems, non-engineering measures should be implemented in conjunction with the runoff allocation and outflow control, and of land development program. By this way, the Keelung River could achieve sustainable management.