Predicting tides at Lakes entrance as part of a flood warning system

Tidal level at Lakes Entrance (Gippsland, Victoria) is an important contributor to flood risk. We used over 12 months of hourly lake level data to identify important tidal constituents and develop tidal predictions using the 'Foreman' tidal analysis and prediction approach. Predicted water levels were compared with actual levels from a flood event in June 2012 to calculate the water level anomaly which allows separation of tidal influence from the effect of other forcings such as riverine inflows, wind and atmospheric pressure. We also compared our tidal predictions with previous tidal analyses to identify changes to tidal behaviour over time. It is likely that tidal behaviour at Lakes Entrance will continue to evolve so tidal prediction equations must be re-calibrated every few years. This is especially important following major flood events or other activity such as dredging, that change the flow of water between the ocean and the Gippsland Lakes. Our analysis suggests that timing and height of water levels associated with tides can be predicted with sufficient accuracy to form part of a flood warning system for the Gippsland Lakes.