Determining target loads of large and small wood for stream rehabilitation in high-rainfall agricultural regions of Victoria, Australia

Wood is an important structural component of many streams, and its reinstatement is increasingly part of river rehabilitation efforts. Determining how much wood to reintroduce, and of what size, can be difficult. A census of the natural wood load was undertaken in two high-rainfall regions of southeastern Australia, to develop a benchmark for use in rehabilitation projects in agricultural landscapes. The contributions of small and large wood and the use of stream characteristics to predict pre-disturbance loading are investigated. Over a 50 m reach, an average wood load of 70.5 pieces was recorded, with a volume of 0.021 m3/m2 and surface area of 0.386 m2/m2. Load was relatively consistent within and between regions and was comparable to loads reported elsewhere, supporting the use of local average loads as a benchmark. Small wood contributed significantly to the number of pieces and surface area of wood within study reaches, but volume was dominated by the contribution of large wood. Correlations between load and stream characteristics are complex and have not been demonstrated to be predictive. Thus, we argue that it is preferable to determine a benchmark from nearby streams in reference condition.