Hydrological Characteristics of Australia: National Catchment Classification and Regional Relationships

A continent-wide classification study of Australian catchments was undertaken to group drainage basins with comparable flow characteristics based on forty metrics from the themes of climate, topography, surface condition and hydrogeology. A principal component analysis reduced the multi-collinear indices to nine principal components (PCs). A fuzzy c-means cluster analysis on the PCs resulted in the delineation of eight subcatchment clusters with similar physiography, and 82.5% of subcatchments displaying a membership coefficient greater than 0.7. Subcatchments with poor cluster membership levels may be significant in highlighting complexity in the interaction between climatic controls and local geomorphological and land use variability. The clusters are distinguished by different attributes in several key subcatchment variables and each group is described in terms of its flow and flood profile. These interpretations are supported by separately derived streamflow signatures from gauged catchments. Cluster and PC distribution mapping revealed distinct spatial and drainage relationships between the subcatchments relevant to the assessment of flood behaviour. The spatial pattern of the river basin regionalisation via physical catchment similarity closely resembles the modified Ko center dot ppen climate classification, with differences highlighting the importance of non-climate characteristics on streamflow behaviour in Australia. The catchment classification is an Australia-wide regionalisation scheme, incorporating datasets with disparate spatial distribution and ungauged subcatchments. This study therefore provides the framework for more detailed streamflow analysis by applying consistent methods across all catchments in Australia, and has implications for flood risk prediction, mitigation and planning.