Abstract
On Nha Trang Coast, in southern of Vietnam, investigation of shoreline change using video-camera technique has been carried out over the period of about one and a half year. Thus, data of shoreline change was obtained two times for the northeast monsoon period and two times for the non-monsoon period. Images on plane coordinate system, which are projected from oblique images of the video-camera system, are utilized to evaluate shoreline variation. During the northeast monsoon period, longshore sediment transport from north to south is dominant; as a result, that causes erosion of sandy beach in the north end area of Nha Trang Coast. Recovery process of shoreline in this area is observed in the nonmonsoon period. In addition, the variation of shoreline is analyzed to obtain longshore sediment transport rate. Characteristics of waves are greatly different between the northeast monsoon period and the nonmonsoon period; hence, it is necessary to change value of depth of closure (DC) for corresponded season. This study determined seasonal variation of depth of closure as well as an ordinary method to obtain a constant value of depth of closure has been also utilized; the difference is clarified.
