The central Australian stream floods of February-March 1967

Abstract

Between February 5 and March 8, 1967, central Australia received some of its heaviest rains on record. Derived from three separate southward intrusions of monsoonal weather, the rains gave total gaugings of 120–350 mm, with some stations receiving overnight falls of over 150 mm. The ensuing floods were the most devastating in the western Lake Eyre basin in living memory. Accurate hydrological data are available only for the Todd and Finke rivers. During the 1967 floods the Todd attained a maximum gauge height of 2.17 m and a mean velocity of 1.95 m/sec; the Finke, a maximum gauge height of 6.95 m. Other major streams flooded to depths of 3–5 m and locally spread to widths of several kilometres. On March 15, floodwaters were observed entering Lake Eyre by way of the Macumba and the Neales. Finke waters did not reach Lake Eyre, being absorbed by the sands of the Simpson Desert. Large-scale ripples (dunes) were preserved on most sand-bed channels at the recession of the floods, indicating that subcritical flow prevailed for most streams. By estimating the Froude number (F) and the Darcy-Weisbach resistance coefficient ( f) for large-scale ripples, mean stream velocities of about 0.8–2.8 m/sec have been calculated for such channels. In contrast, flat-bedded sand with parting lineation was deposited in the middle reach of the Finke. It is estimated that there the Finke attained a mean velocity of about 3 m/sec and a peak discharge of about 1200 m 3/sec.