Rapid assessment of gully sidewall erosion rates in data-poor catchments: A case study in Australia

Knowledge of erosion rates and sediment yields from gullies is critical for the effective prioritisation of management efforts aimed at reducing the impact of gully-derived sediments on water quality. This paper describes a rapid assessment method for estimating sidewall gully erosion rates for already established gully networks. It combines a conceptual-empirical model of the cycle of gully initiation and stabilisation with an easy-to-apply technique for assessing gully extent and dimensions. The method is illustrated using a case study of the Avon-Richardson Catchment of north-central Victoria, Australia. It is estimated that a total of 4.6×10⁶tonnes of sediment have been generated in that catchment from gully erosion since the latest major phase of gullying in the mid 1800s. This is equivalent to 8.9tha^-1y^-1 if sediment generation was evenly distributed spatially and temporally across the 3300km² catchment over 160years prior to 2010. Current rates of gully erosion are estimated to be 4700ty^-1 (equivalent to 1.4tha^-1y^-1). The results are comparable with observed rates of sidewall erosion in the Avon-Richardson Catchment. Further testing is required to build confidence in its applicability to assess sediment yields and for assisting regional authorities to plan remediation efforts.