Dendrochronological Flood-frequency Analysis: An Australian Application

Dendrochronological studies have received little attention in Australia and it appears that the methodology is not well understood. This paper describes dendrochronological techniques available in riparian environments and applies them to a small reach of the Hawkesbury River. Results of field investigations into the relationships between flooding and associated tree-ring variability were used to reconstruct partial duration flood-frequency data. The ring-width chronologies of 39 trees were transformed into three indices that made interpretation with respect to flooding possible: (1) a width-index: (2) an annual-sensitivity (AS) index; and (3) a tilting vector. It was assumed that floods would either suppress growth or alter the annual distribution of new wood about the tree bole. Width-indicies and tilting vectors provided the most reliable flooding information. Much reduced growth rates at low elevations supported initial hypotheses and led to the establishment of a relationship between growth-rate and frequency of inundation. The reconstructed flood-frequency curve closely matched the historical data-set although underestimation occured at higher levels due to limited sample size. Analyses indicate that dendrochronological investigations of exotic riparian trees provide detailed flooding information, but techniques may also be used to provide minimum dates of fluvial landforms and date recent channel changes.     

RURAL AND REGIONAL RESTRUCTURING OF APARTHEID: IDEOLOGY, DEVELOPMENT POLICY AND THE COMPETITION FOR SPACE

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