TEMPORAL VARIABILITY OF CLIMATE IN SOUTHEASTERN AUSTRALIA - A REASSESSMENT OF FLOOD-DOMINATED AND DROUGHT-DOMINATED REGIMES

Inter-decadal periods of high and low food activity have been consider ed to be the dominant factor driving river metamorphosis in catchments along the New South Wales coast. Recent work has questioned the data analysis techniques used in delineating the so-called flood- and droug ht-dominated regimes (FDRs/DDRs). Concerns have also been raised about the validity of invoking a climatic control for river metamorphosis d ocumented during the post-European period, when extensive anthropogeni c alteration of catchment and riparian vegetation has also occurred. T his paper reviews the evolution of the FDR/DDR concept. We examine the evidence for FDRs/DDRs, and highlight problems with the original hydr ological data sets, as well as with the techniques employed in the tim e-series analysis. We discuss conceptual problems encountered in apply ing flood-frequency analysis, and the failure of the proponents of the FDR/DDR theory to consider large-scale climatic circulation patterns and the geographical boundaries of their influence. We conclude that t he validity of the FDR/DDR notion has been seriously over-stated, and that managing rivers on the basis that FDRs/DDRs have occurred in the past, and will continue to occur in the future, is likely to be ineffe ctive.