雲林海岸漂砂研究

Sediment Movement along the Yunlin Coast, Western Taiwan

林宗儀(Tsung-Yi Lin)

《華岡地理學報》 16期 (2003/06) Pp. 25-41

摘要

雲林近岸海域沈積物收入主要來源是來自濁水溪的河川輸砂，其次則是藉沿岸流搬運由北側海域往南輸送的沿岸漂砂，及波浪、潮汐的向岸搬運和離岸風所帶入的沈積物。而沈積物的支出主要是更往南側海域輸送的沿岸漂砂，其次是波浪、潮汐的離岸搬運和向岸風所帶離的沈積物。由於雲林海岸作用有明顯的季節性變化，冬季和夏季的能量和漂砂作用略有不同。
夏季時因受西南風和波浪的影響較小，潮汐的作用特別明顯，漂砂方向主要受到潮流的控制，在漲潮時沿海岸方向，向北北東或東北方向移動，退潮時則往南南西或西南方向，沿岸方向的淨輸砂量不大，主要的漂砂活動有濁水溪的輸砂，和颱風期間波浪對海灘沈積物的離岸搬運。冬季時因受強烈東北季風的作用且波浪較大，漂砂方向除了受潮流的控制外，主要受到風驅流或由波浪所引起的沿岸流所影響，大致是沿著海岸向南或西南方向。因冬季的漂砂量遠大於夏季，其長期年平均的淨漂砂方向應是沿海岸由北或東北向南或西南移動。冬季期間另一重要的漂砂活動是由陸側向海灘吹送的離岸方向風砂搬運，據推估，冬季的風砂搬運量約爲夏季的30倍，在自然環境狀態下，雲林海岸風砂全年平均淨輸砂方向是離岸方向，總量約爲5~8×10^4立方公尺，淨輸砂率爲1.2 ~1.9立方公尺/m/yr。

關鍵字

漂砂 ； 風砂 ； 沈積物收支 ； 沈積物搬運 ； 海岸作用 ； 雲林海岸

並列摘要

Combined with large amount of sediment supplies from Choushui River and vigorous coastal processes, the sediment movement along the Yanlin coast is the most active one in western Taiwan. Based on the sediment and process analysis, an obvious seasonal variation of sediment movement is observed. Summers is the flood season for Choushui River to provide large amount of sediment to the coast, but the net sediment transport by coastal processes is relatively small. The southwestern winds and waves at Yunlin coast are weak in summer, then the coastal sediment transport is dominated by tidal currents. With the to-and-fro tidal movement alongshore, the net longshore transport is small. During the winter, strong winds and waves from northeast are the decisive forces for the sediment moving alongshore from north to the south. Since the longshore sediment transport during the winter is far more than summer, the long-term net longshore transport is to the south. This result had been reflected in the accumulation of sediment at north side of engineering structure that protruding into water. Another important process of moving sediment during the winter is the acolian transport. The net yearly acolian transport volume for the whole shoreline along the Yunlin coast is estimated to be 5~8×10^4 m^3 offshore. The net transport rate is then estimated to be 1.2~1.9 m^3/m/yr.

並列關鍵字

drift sand ； wind-blown sand ； sediment budget ； sediment transport ； coastal processes ； Yunlin coast

參考文獻

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