Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

Flood and drought impacts on the opening regime of a wave-dominated estuary

Paul Rustomji

CSIRO Land and Water, GPO Box 1666, Canberra, ACT 2601, Australia. Email:

Marine and Freshwater Research 58(12) 1108-1119
Submitted: 17 April 2007  Accepted: 2 November 2007   Published: 13 December 2007


Wave-dominated estuaries are affected by floods generated in their hinterland catchments as well as marine tide and wave processes. The interaction of these terrestrial and marine influences controls the opening regime of the estuary. Despite the well documented environmental pressures on estuaries including elevated nutrient loadings and abstraction of river flows, little research concerning the variability and controls on estuary mouth opening regimes exists. From water level observations of Tuross Lake estuary in south-eastern Australia, the estuary’s recent opening regime is reconstructed and shown to vary significantly over time. Floodwaters fill the estuary and scour the estuary mouth, enhancing the exchange of marine water between the estuary and the ocean, which manifests as an increased tidal range within the estuary. Between floods, tide and wave activity caused aggradation of the estuary mouth such that the tidal range within the estuary declined by 0.5–0.7 mm per day as the mouth became more constricted. Under conditions of low river flow, high evaporative losses and seasonal reductions in ocean wave height, the estuary mouth can close completely. Using twentieth century streamflow estimates, it is shown that hydrologic variability is likely to have resulted in large variations in the estuary’s opening regime. Since 2000, there have been relatively few flood-driven scour events and this explains the relatively congested state of the current estuary mouth. Predicted hydrologic changes under enhanced atmospheric carbon dioxide concentrations are also likely to enhance the variability in the estuary’s opening regime.

Additional keyword: intermittently closed and open lakes and lagoons.


Allen R.Pruitt W.1991FAO-24 reference evapotranspiration factors.Journal of Irrigation and Drain Engineering117758773doi:10.1061/(ASCE)0733-9437(1991)117:5(758)

Anthony E. J.Oyede L. M.Lang J.2002Sedimentation in a fluvially infilling, barrierbound estuary on a wave-dominated, microtidal coast: the Oueme River estuary, Benin, west Africa.Sedimentology4910951112doi:10.1046/J.1365-3091.2002.00491.X

Australian Hydrographic Service (2002). ‘Australian National Tide Tables 2002.’ (Australian Hydrographic Service: Wollongong.)

Bell K. N. I.Cowley P. D.Whitfield A. K.2001Seasonality in frequency of marine access to an intermittently open estuary: implications for recruitment strategies.Estuarine, Coastal and Shelf Science52327337doi:10.1006/ECSS.2000.0709

Chiew F.2006Estimation of rainfall elasticity of streamflow in Australia.Hydrological Sciences Journal51613625doi:10.1623/HYSJ.51.4.613

Cooper J.2001Geomorphological variability amoung microtidal estuaries from the wavedominated South African coast.Geomorphology4099122doi:10.1016/S0169-555X(01)00039-3

Dalrymple R. W.Zaitlin B. A.Boyd R.1992Estuarine facies models: conceptual basis and stratigraphic implications.Journal of Sedimentary Petrology6211301146

Davis J. R.Koop K.2006Eutrophication in Australian rivers, reservoirs and estuaries a southern hemisphere perspective on the science and its implications.Hydrobiologia5592376

Elwany M.Flick R.Aijaz S.1998Opening and closure of a marginal southern California Lagoon inlet.Estuaries21246254doi:10.2307/1352472

Erskine W. D., and Warner R. F. (1988). Geomorphic effects of alternating flood and drought dominated regimes on NSW coastal rivers. In ‘Fluvial Geomorphology of Australia’. (Ed. R. F. Warner.) pp. 223–224. (Academic Press: Sydney.)

Franks S. W.Kuczera G.2002Flood frequency analysis: evidence and implications of secular climate variability, New South Wales.Water Resources Research381062doi:10.1029/2001WR000232

Haines P. (2004). Tuross Estuary and Coila Lake Estuary management study. Technical report. (WBM Oceanics Australia. Prepared for Eurobodalla Shire Council.)

Harrold T., Chiew F., and Siriwardena L. (2005). A method for estimating climate change impacts on mean and extreme rainfall and runoff. In ‘MODSIM 2005: International Congress on Modelling and Simulation’. Modelling and Simulation Society of Australia and New Zealand. Available at [Verified 10 April 2007].

Hennessy K., McInnes K., Abbs D., Jones R., Bathols J., Suppiah R., et al. (2004). Climate change in New South Wales part 2: projected changes in climate extremes. Consultancy Report for the New South Wales Greenhouse Office. Climate Impact Group CSIRO Atmospheric Research.

Jeffrey S.Carter J.Moodie K.Beswick A.2001Using spatial interpolation to construct a comprehensive archive of Australian climate data.Environmental Modelling & Software16309330doi:10.1016/S1364-8152(01)00008-1

Jones M.West R.2005Spatial and temporal variability of seagrass fishes in intermittently closed and open coastal lakes in southeastern Australia.Estuarine, Coastal and Shelf Science64277288doi:10.1016/J.ECSS.2005.02.021

Kench P.1999Geomorphology of Australian estuaries: review and prospect.Austral Ecology24367380doi:10.1046/J.1442-9993.1999.00985.X

Kennish M. J.2002Environmental threats and environmental future of estuaries.Environmental Conservation2978107doi:10.1017/S0376892902000061

Kraus N.Militello A.Todoroff G.2002Barrier breaching processes and barrier spit breach, Stone Lagoon, California.Shore and Beach702130

Loneragan N. R.Bunn S. E.1999River flows and estuarine ecosystems: implications for coastal fisheries from a review and a case study of the Logan River, southeast Queensland.Australian Journal of Ecology24431440

Mackenzie D., Bray G., Richardson P., Lingard J., Lingard J., Maher B., et al. (2002). Opening regimes in five small, contrasting ICOLLS of the Batemans Bay (NSW) area. In ‘Proceedings of the Coast to Coast Conference 2002’. (Coastal Zone Cooperative Research Centre.) Available at

Manly Hydraulics Laboratory (2005). Wave statistics. Technical report, Manly Hydraulics Laboratory, Sydney.

McInnes K.Hubbert G.2001The impact of eastern Australian cut-off lows on coastal sea levels.Meteorological Applications8229243doi:10.1017/S1350482701002110

Nanson G. C.Hean D.1985The West Dapto flood of February 1984: rainfall characteristics and channel changes.The Australian Geographer164249258doi:10.1080/00049188508702880

O’Connell D., and Wiltshire G. (2005). The mysteries of closed coastal lakes “myths busted”. In ‘New South Wales Coastal Conference, 8–11 November, Narooma’. Available at

Peel M. C., Chiew F. H. S., Western A. W., and McMahon T. A. (2000). Extension of unimpaired monthly streamflow data and regionalisation of parameter values to estimate streamflow in ungauged catchments. Report for National Land and Water Resources Audit Theme 1: Water Availability project. Centre for Environmental Applied Hydrology, University of Melbourne, Melbourne.

Phinn S.Hastings P.1992Southern Oscillation influences on the wave climate of south-eastern Australia.Journal of Coastal Research8579592

Phinn S.Hastings P.1995Southern Oscillation influences on the the Gold Coast’s summer wave climate.Journal of Coastal Research11946958

Pittock A. B.1975Climate change and the pattern of variation in Australian rainfall.Search6498504

Pollard D. A.1994Opening regimes and salinity characteristics of intermittently opening and permanently open coastal lagoons on the south coast of New South Wales.Wetlands (Australia)131635

Ranasinghe R.Pattiaratchi C.1999The seasonal closure of tidal inlets: Wilson Inlet a case study.Coastal Engineering Journal373756

Ranasinghe R.Pattiaratchi C.2003The seasonal closure of tidal inlets: causes and effects.Coastal Engineering Journal45601627doi:10.1142/S0578563403000919

Ranasinghe R.McLoughlin R.Short A.Symonds G.2004The Southern Oscillation Index, wave climate and beach rotation.Marine Geology204273287doi:10.1016/S0025-3227(04)00002-7

Reddering J. S.Rust I. C.1990Historical changes and sedimentary characteristics of southern African estuaries.South African Journal of Science86425428

Roy P. S.Peat C.1975Bathymetry and bottom sediments of Tuross Estuary and Coila Lake.Records of the Geological Society of New South Wales18103134

Roy P. S.Williams R. J.Jones A. R.Yassini I.Gibbs P. J.Coates al.2001Structure and function of south-east Australian estuaries.Estuarine, Coastal and Shelf Science53351384

Rustomji P. (2003). Holocene geomorphology of the Macdonald and Tuross Rivers. PhD Thesis. Australian National University, Canberra.

Shuttleworth B.Woidt A.Paparella T.Herbig S.Walker D.2005The dynamic behaviour of a river-dominated tidal inlet, River Murray, Australia.Estuarine, Coastal and Shelf Science64645667doi:10.1016/J.ECSS.2005.04.007

Steffe A., Murphy J., Chapman D., Barrett G., and Gray C. (2005). An assessment of changes in the daytime, boat-based, recreational fishery of the Tuross lake estuary following the establishment of a recreational fishing haven. Fisheries Final Report Series 81. NSW Department of Primary Industries, Sydney.

Thom B. G.Bowman G. M.Gillespie R.Pollach H. A.Barbetti M.1981Progradation histories of sand barriers in New South Wales.Search12323325

van de Kreeke J.1967Water-level fluctuations and flow in tidal inlets.Journal of the Waterways and Harbors Division, American Society of Civil Engineers497106

Whetton P.Fowler A.Haylock M.Pittock A.1993Implications of climate change due to the enhanced greenhouse effect on floods and droughts in Australia.Climatic Change25289317

Whitfield A. K.1992A characterization of southern African estuarine systems.South African Journal of Aquatic Science1889103

Whitfield A. K.1997Fish conservation in South African estuaries.Aquatic Conservation7111

Young G. C.Potter I. C.Hyndes G. Lestang S.1997The ichthyofauna of an intermittently open estuary: implications of bar breaching and low salinities on faunal composition.Estuarine, Coastal and Shelf Science455368doi:10.1006/ECSS.1996.0165

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