Turbidity-based erosion estimation in a catchment in South Australia

An erosion estimation technique was developed in this study based on turbid ity and sediment sampling data in a small catchment in South Australia. Sev eral data sets, derived from the time sequence in which the data were colle cted, were used to develop a number of turbidity and suspended sediment rel ationships. These relationships were then used to estimate erosion from the catchment. The variability in sediment load estimation using different rel ationships, and how these relationships impacted on load estimation, were a nalyzed in detail. The study estimates erosion on a storm basis using detai led sediment sampling and turbidity data. Storm sediment loads were then ac cumulated to derive annual load, which distinguishes this study from volume based sediment studies. The study found that large storms dominate erosion in the catchment, and erosion rate depends more on peak storm flow than ot her hydrological variables. A relatively low annual erosion rate from the c atchment was found, which is consistent with studies in other Australian ca tchments. The study found that, to establish a sound relationship between s uspended sediment and turbidity for a catchment, it requires extensive data collection of large as well as small storms at short time intervals, a sto rm-based erosion estimation approach, and a data set that is used for inter polation rather than extrapolation. Erosion estimation based on infrequent, non-storm based or extrapolated data is exposed to potentially large error s, and the results may only be relied upon as a general guide rather than s erious estimation of catchment erosion. (C) 2001 Elsevier Science B.V. All rights reserved.