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。

According to the 2013 water management algorithms and analyses on cross-section data of the river system, the results showed that several river sections failed to meet the flood control standards. They are listed as follows: the right riverbank of the estuary, river sections near Shezi, Quchi and Zhitan river sections of the Xindian Creek and confluence of the Jingmei River, and Hengxi River. Compared with simulation results obtained from the preliminary project, the flood release capability of most rivers met the flood control standards. Xindian Creek and Jingmei River showed the largest differences in water level changes over the years. Danshuei River exhibited the highest water level in 1969 and the lowest in 1989 because of the sand mining operations in the early days and their subsequent ban. The results for the estimates of the amount of soil and sand produced in the project area revealed that the average annual soil and sand production from 2003 to 2013 was approximately 1.8047 million cm3. The amount of soil and sand outflow caused by structural collapse was 1.1449 million cm3, and the amount of soil that was eroded from the slopes was 0.6598 million cm3. Assessments of the effect of transverse structures on sand flow in the rivers showed that scours and fills were predominately observed in the bridges and near the weirs. Regarding the one-dimensional sand flow simulation, the project began with a sand flow characteristics analysis before the NETSTARS model was employed to analyze the scour and fill situation of the rivers because of the short and long-term water flow during recurrence intervals. Relevant stability indicators were used in the river stability assessment to evaluate the scour and fill stability of the rivers. Dredging suitability assessments were performed for each river section, and recommendations were provided regarding the river sections in which two-dimensional scour and fill simulations could be performed. For this project, a “river scour-and-fill display” assignment was added. In the assignment, a display platform and database called “three-dimensional geographic information system of the Danshuei River System” developed by the 10th River Management Office were used as the basis to develop a system that enabled users to search cross-sectional data of the river system over the years and to compare the amount of scours and fills. Regarding the mapping and display of the river sections prone to changes, three river sections in the Sanxia River that were prone to changes were used, and a surface light detection and ranging method was adopted to perform topographic mapping, which can be used as the basis for river change comparisons in the future.