由於漂沙因水流而移動的關係複雜,所以 至今對於漂沙量之計算,尚未有完整之理論基 礎。但是在水理方面的理論,則已經有了很好 的模擬;周及林(1991)利用Bagnold(1966)總輸沙量觀 念估算前灘區漂沙的運移量,但受限於波浪理 論模擬之極限,未能計算整個海灘斜坡面漂沙 的運移情形。根據Ho & Meyer(1962)指出波浪回降 時水流運動依自由落體運動情形回沖,故本研 究主要係依自由落體運動來繼續模擬前述波浪 理論所不能模擬的部分,亦即圖一中A點以下斜 坡上水流運動情形;並配合Bagnold輸沙模式完成 整個海灘斜坡面漂沙運移的數值模式。另外並 依據本數值模式以Bretschneider方法來模擬實際颱風來襲時,海灘地形的變化。再且因實際波 浪多以不規則波的形式存在,故利用JONSWAP spectrum依本數值模式來模擬不規則波造成海灘 地形的變化情形。 Owing to its complicated phenomenon, the onshore- offshore sediment transport has yet had a sound theory. On the other hand, the theory of the wave runup has been studied and some fairly good simulations have been formed. According to the hydraulic model, Chou & Lin (1991) used Bagnold's total load concept to establish a numerical model to calculate the sediment transport rate on the swash zone. But, under the restriction of the shallow water wave theory, this model can only be used on a limited area. Ho & Meyer (1962) had pointed out that the wave backwash motion is like the movement of a free falling body. This study is thus based on such concept to develop a complete numerical model to compute the sediment transport on a sloping beach. Also Bretschneider method is used to simulate a typhoon passing through Taiwan. The causing sedimentation due to such typhoon is calculated by the developed numerical model. Using JONSWAP spectrum coped with our model, the sedimentation on a beach due to random waves is thus studied.