In this thesis the hydrodynamic behaviour of an idealised relatively short tidal estuary is studied using a cross-sectionally averaged model, i.e. a one dimensional model. The geometry of the estuary is simplified and only the hydrodynamic processes are considered. This model is used to gain insight in the behaviour of currents and water levels influenced by a movable barrier situated in the estuary. It is investigated whether shifting the motion of the barrier in time influences the sedimentation in the embayment.