本研究根據淡水河河口歷年資料進行分析與討論，並探討台北港興建對淡水河輸砂及排洪之影響。研究結果顯示挖子尾砂嘴地形演變及河口之河槽斷面皆有逐漸淤積的現象，且砂嘴處灘線逐年變動並持續溯河延伸及外擴之趨勢。觀測點T00至T10A，整體呈現淤積趨勢；其中T00至T05間，呈現高度變動狀態且整體呈現淤積，部分區域亦有侵蝕現象，主深槽位置逐年移動且有深淺變化；T06至T10A區段呈現逐年淤積趨勢，主深槽之位置與深度無明顯變動，為較穩定之區域。 淡水河河口處之粒徑以中砂為主，河口內左岸顆粒較細，此區為水筆仔生態保護區，含泥量較高；右岸顆粒較粗，此區為河口區之主深槽，且淡水渡船頭亦在此岸。淡水河底床為中砂粒徑範圍處，與水下砂丘主要分布區域相吻合。淡水河底床最大砂丘在河口處，高度約1 m，砂丘長度為25-70 m。砂丘砂粒往下游運移證明了砂源來自淡水河上游；臺北港近北側防波堤之淺水區逐年向岸侵蝕，而灘線則向海淤積。;This research analyzes the chronological data of Tamsui River′s estuary, it also explores the influence cast on sediment transport and drainage by the construction of Taipei Harbor. The research result shows that the phenomenon of gradual sediment appears in the landscape change of the sand spit in Waziwei and in the sections of the river month. In addition, the beachline in the sand-spit area changes annually and continues to extend upstream and expand outward. From T00 to T10A, there shows a trend of sediment. Between T00 to T05, there are a highly varying condition and the overall sediment, and there is also erosion in some areas. Main channels′ locations move every year and the channels′ depth varies. Between T06 to T10A, the trend of sediment also appears. The main channels′ location and depth are steadier. The sand at the estuary is mostly medium sand. The sand particle is thinner on the left bank within the estuary. This area is the ecological reserve containing high mud content. The grain size of the sand on the right bank is coarser. Tamsui Ferry Pier is located at the main channel. On the riverbed, the range wherein the medium sand gathers matches the area wherein underwater sand dunes mainly spread. The largest sand dune on the riverbed is located at the estuary; its height is about 1 m and its length is about 25-70 m. This research proves that the sand source is from upper reaches of Tamsui River, the shoal waters by the breakwater near the north side of Taipei Harbor erode the shore year by year, and the beachline expands outward to the ocean with sediments.