Sediment Transfer through the Fluvial System (Proceedings of a symposium held in Moscow, August 2004). IAHS Publ. 288, 2004, 13–20

1 State Forests of New South Wales, Research & Development Division, PO Box J19, Coffs Harbour Jetty, NSW 2450, Australia

2 Division of Geography F09, University of Sydney, NSW 2006, Australia

Abstract Sedimentological, stratigraphic and radiocarbon analyses of flood plain sediment indicate that flood plain pockets of Bruces Creek, a sand-bed forest stream, were completely removed by a catastrophic flood around 1000 years BP. The present flood plain redeveloped by lateral migration prior to 575 years BP and was colonised by an emergent Eucalyptus forest and Tristaniopsis laurina (Water Gum) trees. Since 300 years BP, channel stability has been controlled by riparian vegetation and large woody debris (LWD), as indicated by obliquely accreted fine-grained sediment deposits on the channel banks. This work indicates that sediment transfer through small sand-bed forest systems is minimal during extended periods of vegetation-controlled channel and flood plain stability. However, episodic high-energy catastrophic floods can exceed thresholds of channel stability, totally destroy alluvial landforms and the flood plain forest, and result in the delivery of massive pulses of sediment to the channel.

Key words catastrophic erosion; catastrophic floods; flood plain stripping; riparian vegetation; sediment transfer; southeastern Australia