Syawaluddin Hutahaean
This research is working on an assumption that longshore sediment transport is the primary cause of the changes in coastline. Longshore sediment transport equation of some researchers, such asKomar, P.D., (1998), Shore Protection Manual (SPM), (1984), Van Rijn, Leo C. (2013), MillHomens, J., Ranasinghe, R., Van Thiel de Vries, J.SM. and Stive, M.J.F., (2013), is the sine function of the breaker crest line angel where the value of Longshore sediment transport is zero or no longshore sediment transport if the breaker crestline is parallel to or forming zero angle against the coastline. In other words, in a stable coastline, the tangent of breaker crestline is similar to the tangent of the coastline. This condition becomes the basis of salient equation in this research. This research aims at obtaining the method of salient height Ys for a breaker length L, at a breakwater distance X. This research is the continuation of a previous research by the writer where in the previous research polynomial approach was applied where the value of the polynomial coefficient is obtained by applying stable coastline equation on various points (boundary point) on the original coastline. In the previous research, the difficulty was found in determining boundary points. In this research, salient equation is also approached with polynomial, where polynomial coefficient is obtained by using Least Square Weighted Residual Method with Galerkin procedure (Stassa, F.L. (1985)), whereas the tangent of salient is approached with a polynomial equation using five sample points.
Penerapan Karya Tulis
Offshore breakwater is a breakwater constructed parallel with the coast. Even though it is called offshore breakwater, the position of the construction is quite close with the coast, where the construction efficiency is very much determined by the distance between the breakwater and the original coastline. On the coast protected by offshore breakwater, sediment deposit will be formed which is called salient. The success of coastal protection using offshore breakwater is determined by salient Ys that that was formed, where the height of the salient is determined by the length of breakwater Ls and the distance between breakwater and the original coastline or breakwater distance X. Considering that breakwater is constructed quite close with the coast where the crestline is almost parallel with the coast or the wave direction is almost perpendicular to the coast, thereforein this research a breakwater is developed for a wave that is perpendicular to the coast.