Laboratory study of sand bar development at a river entrance

River mouth topography changes continuously due to the actions of waves and river flow. Under the combination effect of waves, tide movement, long-shore and cross-shore current, and river flow, sediment is transported and deposited at the river mouth, forming sand bars at this area. Sand bars at river mouth influence extremely to river flow features in the river, obstruct navigation and flood discharge. The feature of waves, river flow and bed layer material are the main factors that relate directly to the characteristics of sand bar. However, it can prevent the river from salinity intrusion, and be flushed easily in flood season. Understanding sand bar formation at river mouth and its size are necessary for flooding and navigation control. In this study, the actions of river flow are eliminated because river discharge is often small in the winter this is good condition for sand bar formation at river mouth. The development of sand bar is highly considered by a lot of managers, engineers both in the elevation and horizon. This study will show the estimation about the height and width of sand bar at river entrance as well as its profile area. A field observation on the formation process of sand bar was carried out at river mouth after being flushed by the flood in the river to verify laboratory experimental results.