Sediment processes in a coastal lake : Causeway Lake, the Capricorn Coast

The Causeway Lake represents an artificially created lake in the estuary, having restricted connection with the sea by the bridge width and sill elevation. It is located on the Capricorn Coast, Queensland. During the 65 years of the lake's life time, the siltation has significantly reduced usability of the lake as a recreational area for fishing and sport activities. It is no longer able to be used by yachts or motorboats as the large area of the lake has a depth below 0.5m The paper discusses methodology of the evaluation of the siltation of the lake, sources and probable quantities of the sediment entering the lake. Based on this bathymetry data the average sedimentation on the 66 ha of the lake was about 2500 m'ly. Measurements of diseharges under the bridge during flood and ebb tides together with measurements of suspended sediment concentrations concluded that about 1000 m'ly can be transported into the lake by tide currents when tide ranges exceed the bridge sill level. The average annual sediment transport from the catchment is in the order of 1100 m'.