新竹海岸地形之變化特性及其與風速相關性之研究

Abstract

海岸地形變化是自然的現象，其主要的外力便是波浪。海岸地形侵淤變化量的估算是研究海岸地形變遷的重要參考指標，傳統由風速來推算波浪，再由波浪推估地形變化量的過程太過繁複，容易累積較多的誤差量，或者有波浪資料無法長期不間斷收集而缺少的問題。有鑑於此，本文便利用輸入與輸出間類似黑盒分析的概念，發展一套簡單、易用且可準確由風速來推估海岸地形侵淤變化量的方法。 本文首重於新竹海域相關環境資料的蒐集，藉此瞭解過往的相關調查及研究成果，並對整個研究區域有一全盤的瞭解與認識。第二便針對整個研究區域，以實地測量資料進行海岸地形侵淤變化的分析與探討，並計算出整體區域及每一分區的地形侵淤變化量，歸納出整個區域的地形變化趨勢。第三則是透過回歸分析的方式，找出風速與地形侵淤變化量間最佳的關係，並獲得最佳之預測方程式。最後再進一步的探討不同回歸式參數的可行性。 本文最後獲得的最佳預測方程式，具有準確度高與容易使用的特性，有助於新竹地區海岸地形侵淤變化量的估算與預測。而本文所使用的概念與分析方法，並無地域性之限制，其他研究者可以仿效本文的分析方法與流程，建立起其他區域預測海岸地形變化量之專屬模式。

The coastal topographical evolution resulting from dominantly external force by waves is a natural phenomenon and can be well evaluated by bathymetrical volume changes. Traditional physical models to estimate bathymetry changes are so complex and academic that they are not popular to marine engineers. This paper investigates bathymetrical changes and their relationship with wind speeds. Three procedures are presented to find the solution for this problem. The first step is to collect different kinds of background data at Hsinchu waters, including four-year bathymetrical measurements, wind speeds, and river sediments etc.. The second step is to calculate bathymetrical change in all grid cells from any two data sets of beach bathymetry using ‘surfer’ software. Bathymetrical changes in each cell and in the whole region are discussed. Finally the regression method is used to relate beach bathymetrical changes to wind speeds. Three kinds of models with high accuracy are proposed to forecast bathymetrical changes when wind speeds are given. The presented procedures can be easily applied to other coastal regions to set up their local models to forecast bathymetrical changes.