圖書典藏及影音數位平台

淡水河系自78年禁止採砂後部分河段已有逐漸回淤之情況，部分河段亦因河道轉彎、支流匯入及灘地陸化等因素改變流路影響河防構造物安全，本計畫透過水理輸砂數值模式進行分析，了解淡水河系各河段之沖淤趨勢析，評估各河段的沖淤潛勢，以瞭解河道長期穩定程度與未來變動趨勢等河川特性，進而提出治理及疏濬對策，以供本局未來河川治理之參考。

Compared to the hydraulic analysis done in 2013, the latest one conducted in 2015 shows insignificant changes. The Tam-Sui River upstream cross-sections have been qualified to reach the required standard while and the Jing-Mei Creek Cross-section M26 also reach the standard that it failed in terms of the freeboard height tested in 2013 and 2014. The upstream of the Erchong Floodway at the cross-section F12 was tested in 2014 and failed in freeboard height, but the verification done in 2015 shows all the Floodway satisfied the standard and no major changes were found. Typhoon Soudelor hit Xiulin Township located in Hualien County on 8th of Aug 2015 and caused massive hazards such as landslides and debris flows over Wulai District of New Taipei City. Moreover, the rise of Xindian Creek water level caused certain damages as well. Based on satellite images took in 2015, the reevaluation for the sediment yield using 1-D mobile-bed hydraulic models has been performed and used for analyzing scour/deposition potential and river channel stability. The sediment transport modeling cases with design flows of multiple recurrence periods and historic long-term flows reveal relatively small changes in channel bed elevation Tamsui River，Chingmei River, Yongding River and Heng River. On the other hand, the models show ±3-meter invert elevation changes for Dahan River and deposition of 2 m over the upstream of Keelung River. Certain tributaries like Xindian River and SingSin River (particularly downstream of the Cross-section S19) overall are also suggested to be significant in bed mobility. The bed stabilization index is adopted to evaluate the Tam-Sui River system. The evaluation results show that the Chingmei River、SingSin River and Hengxi are relatively stable comparing to Tamsui River, Dahan River, Xindian River and Keelung River. It also shows in general that the rivers are potentially unstable from bank to bank and more stable upstream. On basis of this study, eight potential dredging regions are preliminarily proposed as follows: 1.Convergence of Dahan River to Fuzhou Bridge 2.GanYuan Bridge to Sanying Bridge 3.Shetzu Bridge to ZhouMei Bridge 4.MinCyuan Bridge to ChengGong Bridge 5.YongFu Bridge to SiouLang Bridge 6.ZhiTan Weir to QuChi Weir 7.SingSin Bridge to BaAn Bridge 8.DaLi Bridge to WanTanZai