Waterfalls, floods and climate change: evidence from tropical Australia

Sediments preserved at the base of rare types of waterfalls provide records of terrestrial floods to 30 kyr or more, being approximately 6-10 times lo nger than that usually obtained from the traditional slackwater method. The se coarse-grained sand deposits form ridges and levees adjacent to plunge p ools at the foot of unindented escarpments and within gorge overflow bedroc k channel systems. The extension of palaeoflood records into the Late Pleis tocene allows comparisons to be made between periods of extreme floods and dramatically different climatic regimes. Our results highlight that the las t 30 kyr were dominated by alternating periods of extreme and relatively lo w magnitude floods that correspond to particular climatic regimes. Recent p redictions from Global Climate Models suggest that tropical regions will ex perience dramatic increases in the frequency and magnitude of extreme flood s under a future altered climate. Plunge-pool palaeoflood records can be us ed to at least partially test such predictions by determining whether simil ar previous climate/flood associations have occurred within a region. (C) 1 999 Elsevier Science B.V. All rights reserved.