A physical classification of Australian estuaries

The need for practical estuarine classification schemes as resource management tools is becoming more apparent as development, population growth and pollution in the coastal zone increase the pressure on estuarine systems worldwide (Bucher & Saenger, 1991; Saenger, 1995). In order to properly conserve and manage estuarine resources across their entire spectrum, a comprehensive understanding is needed of the geomorphic and hydrological processes occurring in estuaries, together with their effect on estuarine ecology. Various schemes have been developed to aid the recognition of different estuary types, simplify their description and make possible the transfer of knowledge between estuaries with similar characteristics. In a review of estuarine classification schemes, Ferguson (1996) described the different approaches used in estuarine classification around the world, and highlighted some of the key aspects of Australian estuaries that should be considered when developing a biologically relevant physical classification scheme (Table 1). Most existing classification schemes have focused on geomorphic and/or hydrologic conditions without considering their effect on habitat types and ecology, and very few have included any reference to the evolutionary stage (or maturity) of estuaries which influences both estuarine hydrology and ecology (Roy, 1984).