The Causeway Lake having an area of about 86 ha represents an artificially created lake in the estuary having restricted connection with the sea by the bridge width and bridge sill elevation. It is located on the Capricorn Coast, Queensland. The lake is a sink for suspended sediment transported from the sea by the tidal currents, as well as for sediment transported from the catchments by the creeks when the intensity of the rainfall is sufficiently high. During the 65 years, since the lake creation, the siltation has significantly reduced usability of the lake as a recreational area for fishing and sporting activities. It is no longer accessible by yachts or motorboats because of the large area of the lake which has a depth below 0.5m.The report discusses the implementation of a numerical model RMA, its calibration and results of simulation of the Causeway Lake to evaluate sedimentation processes in the lake. Sedimentation of the lake after 5 and 10 years has been analysed for 4 possible dredging scenarios involving dredging the whole lake or its part and compared with the situation "do nothing" as a scenario 1. --abstract.