The central coast of Vietnam has more than sixty inlets and river mouths discharging into the East Sea. They are often unstable due to entrance shoaling, channel migration and seasonal inlet closure and breaching. These phenomena cause a number of social and environmental problems, such as risk of flooding in the low lying coastal plain, negative impacts on navigation, fisheries and changes to the water environment and ecological system and thereby harming the social-economic development of the region. Using river flow for flushing sediment accumulation at the inlet mouth and in the inlet channel of a tidal inlet system is an alternative non-structural solution that may be used in micro tidal inlets in a wave dominated environment. In this paper, using river flow for flushing an unstable inlet will be simulated in a series of simulation scenarios using process-based modeling (Delft3D) in order to estimate the effectiveness of the solution and to find the optimum way in using river flow for flushing. The model results show that with the same amount of flushing volume, the scenario that has a longer flushing duration and a sufficient flushing discharge is more efficient than the scenario that uses a high flushing discharge over a short duration. This means that the flushing efficiency is closely related to the flushing duration rather than the flushing discharge
