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 longer than that usually obtained from the traditional slackwater method. These coarse-grained sand deposits form ridges and levees adjacent to plunge pools at the foot of unindented escarpments and within gorge overflow bedrock channel systems. Our results are derived from three separate widely distributed stream catchments in the Top End of the Northern Territory. Two distinct episodes of flooding are recorded at all three sites. The earliest during the last glacial maximum (18 — 23 kyr — calendar years) and the most recent during the Holocene climatic optimum (4 — 8 kyr — calendar years).

Enhancement of the monsoon during the LGM possibly resulted from increased pressure gradients between northern and southern Australia. This may have involved the broadening and intensification of the Pilbara and Cloncurry heat lows of Western Australia and Queensland, respectively, across to the Top End of the Northern Territory. Strengthened anticyclogenesis across southern Australia combined with the increased continentality of northern Australia could have resulted in a stronger temperature gradient between the two regions causing extra-tropical cold fronts to be displaced further north towards the heat trough and into a moister air mass resulting in convection. While such mechanisms are a feature of tropical Australia’s climate today they more have been more active during the LGM resulting in a steeper meridional pressure gradient causing the monsoon to intensify but in a more latitudinally restricted region.