Characteristics of Tasmanian estuaries and catchments : physical attributes, population and land use

Estuaries are the interface between the sea and drainage from the land. They can be severely affected by human activities within the catchment. Little is known of the conservation status of Tasmania's estuarine environments. This research is part of an Ocean Rescue 2000 (0R2000) funded project titled 'Regional classification of Tasmanian coastal waters - stage 2, estuaries'. The aim of this research was to augment available data on Tasmanian estuaries by deriving data on the physical attributes and human land use of the catchments of Tasmanian estuaries, and to rank catchments according to their conservation status and degree of human impact. The data derived complements the concurrent survey of estuarine biota and habitats being done as the major part of the 0R2000 project. The thesis mapped the catchments of 122 estuaries identified around the coastline of mainland Tasmania and the Bass Strait islands. These catchments were classified into five groups based on the physical attributes derived for each catchment. The division largely reflected the unique hydrological characteristics of the Tasmanian environment. Catchments in the west and south are characterised by high annual rainfall and high runoff. Catchments in the north-west and south-east have moderate rainfall and runoff, while catchments in the east, north and on the Bass Strait islands are relatively dry. Land clearance and broad categories of land use were determined for 60 catchments using available data derived from satellite images. Tasmanian catchments are highly conserved in comparison with most mainland states of Australia. Eleven out of these 60 catchments can be considered to be pristine with little human impact on the catchment or estuarine conservation values. More than 50% of all catchments are relatively uninhabited, particularly those catchments in the south and west of the state. However a small number of catchments are severely impacted by large scale land clearance and many others are threatened by human impacts. The degree of land clearance and human developments was found to increase greatly with proximity to estuaries. The highest levels of land clearance, population and urban development were detected in catchments along the south-east, east and north coasts of Tasmania.