Spatial and temporal variations of suspended sediment responses from the subtropical Richmond River catchment, NSW, Australia

Shahadat Hossain, Bradley Eyre and David McConchie

Abstract

Suspended sediment exports from the Richmond River catchment were examined during 2 hydrological years (1994–96). On a yearly basis, the Richmond River catchment produced <2% suspended sediment load during dry seasons, whereas about 75–91% of the yearly suspended sediments were exported during floods which occurred <5% of the year. Annual suspended sediment exports from the Richmond River catchment varied more than 7-fold from dry year to wet year. Among the 3 major subcatchments, Richmond and Wilsons River subcatchments generated >93% of the suspended sediment load, while sediment exports from the Bungawalbin Creek subcatchment always remained low due to its flat topography and extensive forest coverage. Suspended sediment hysteresis patterns exhibited a clockwise response for 2 steep and less forested subcatchments and an anti-clockwise response for relatively low gradient and more forested subcatchment during all flood events. Land use changes in the Richmond River subcatchments indicate a possible increase of suspended sediment load of about 6-fold from their pristine condition.

Australian Journal of Soil Research 40(3) 419 - 432 (2002) doi:10.1071/SR01041