Magnitude-frequency analysis of suspended sediment loads in the subtropical Richmond River basin, northern New South Wales, Australia

Data from coastal northern New South Wales, Australia, are used to provide an analysis of magnitude and frequency characteristics in a subtropical river. Over a 14-year period, annual discharge varied by 26 times, suspended sediment (SS) load varied 910 times from 668 t to 607 671 t (mean = 105 6201 year"1 ) and 90% of the SS load was transported in only 2.3% of the time. The 4000^-999 Ml day"' discharge class appears to be most effective for S S transport. The centroid of the annual series (4500 Ml day"1 or 52 m3 s"1 ) has a return interval of 1.01 years. Discharges in this class occurred for 68 days (an average of five days per year) and carried 50 857 t SS (3.4% of the total). There may be multiple effective discharges that may be verified by channel features. Future field studies are planned to test this hypothesis.