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 x 10(6) tonnes 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 8.9 tha(-1) y(-1) if sediment generation was evenly distributed spatially and temporally across the 3300 km(2) catchment over 160 years prior to 2010. Current rates of gully erosion are estimated to be 4700 ty(-1) (equivalent to 1.4 t ha(-1) y(-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. (C) 2010 Elsevier B.V. All rights reserved.