圖書典藏及影音數位平台

莫拉克風災後大量土石堆積改變河道本身輸砂條件，有必要針對北港溪、八掌溪、朴子溪、急水溪水系及轄管區域排水現況河道進行相關檢討，以瞭解整體河道特性、輸砂變化、環境生態影響、加速土石去化等面向，掌握變動趨勢以利未來疏濬工程辦理及整體河道治理上之規劃評估。

Since 2007, a comprehensive dredging project has been undertaken on Beigang River, Puzi River, Bazhang River, and Jishui River. Typhoon Morakot in 2009 and Typhoon Kong-rey in 2013 caused severe damage in Southern Taiwan, including Yunlin, Chiayi, and Tainan. Persistent torrential rain caused avalanches and landslides in the upstream jurisdiction areas of the Fifth River Management Office, Water Resources Agency, Ministry of Economic Affairs. The most severe avalanche and landslide occurred in the Beigang and Puzi River Basins. Heavy rain in the upstream areas brought mud and rock to the downstream areas and forced river channel patterns in the downstream areas to change. As a result, dike revetments and abutments were damaged and debris blocked river channels. In recent years, earthquakes, typhoons, and floods resulted in a large amount of loose sand and gravel, which substantially affected the features and stability of river sediment transport. Soil erosion and deposition in the Fifth River Administration Office jurisdiction areas have critically influenced river channel stability and flood control and safety. Sediment transport information is a crucial reference for managing rivers and riverbed erosion. Dredging operations and river channel change following the dredging operations may influence flood control and safety as well as the natural environment. Therefore, the dredging effectiveness in the Fifth River Administration Office jurisdiction areas in recent years must be assessed and hydrography, flood control, and river-crossing structure safety must be reviewed. Furthermore, dredging strategies should be formulated to serve as a reference for relevant authorities and to achieve flood control, disaster mitigation, and riverbed stability. In addition, in recent years, typhoon disasters have brought a large amount of debris that changed river-sediment transport. Therefore, the current situation of river channels must be reviewed to understand the overall characteristics of the river channels and change in sediment transport as well as to help evaluate and plan overall river management in the future. In this project, the standard operating procedure (SOP) for a dredging plan was established. First, for a wide scope of river channels, preliminary information were collected and river segments requiring dredging were analyzed. The preliminary information included river erosion and sedimentation over the years, river channel change, dredged locations over the years, and river segments prone to damage. According to the investigation, river segments requiring dredging were first determined. In addition, the ability of river channels to relieve floods and long-term river erosion and sedimentation were investigated. Those river segments that could not relieve floods and were easily silted as well as river segments whose river channels deviated from their usual routes and easily damage embankments should be dredged.