Geomorphology of Australian estuaries: Review and prospect

Abstract

Over the past 30 years there has been a wealth of research examining the geomorphology of Australian estuaries. This paper reviews the major regional controls on estuarine geomorphic development and discusses the focus of research efforts to understand estuarine evolution, configuration and processes controlling geomorphic development and change. The presence and position of estuaries along the Australian coastline is controlled by large‐scale climate‐led changes in sea‐level, the antecedent structure of the coast and tectonic activity. The configuration of Australia’s estuaries is controlled by a number of environmental factors identified by Jennings & Bird (1967) including climate, oceanographic regime, sediment availability, structure and mineralogy, and tectonics. Interaction of these factors produce a range of estuarine configurations around the Australian continent from wave‐dominated, microtidal, bar‐built estuaries in the south to low energy macrotidal estuaries in the north which have produced extensive low‐lying coastal plains. The principle focus of geomorphologists during the past 30 years has been understanding the medium to long‐term development of estuaries in response to fluctuating sea‐level over the past 125 000 years. Classifications and models of estuarine development and associated biological community response to estuary development have been identified based on lateral and vertical sedimentary sequences. Results have provided essential information on the physical resources and characteristics of estuarine systems including the distribution of sediment facies that host a variety of different ecological communities. There has been a paucity of research examining contemporary processes controlling geomorphic change in Australia’s estuaries. A morphodynamic approach to the study of estuaries is advocated that evaluates morphology‐process responses as estuaries evolve. This approach requires increased research efforts to identify regional differences in estuarine geomorphic development, hydrodynamic processes and sedimentation. It is also advocated that studies examine how the morphodynamic behaviour of estuaries over thousands of years has influenced estuary ecology. Such studies will provide a more complete understanding of the factors influencing the morphology and ecology of contemporary estuaries.