South-east Australia's forest regions harbour rich endemic biodiversity as well as natural resource value in the form of timber that supports an important forestry industry. Forestry operations may impact on aquatic communities by increasing sediment input into streams beyond natural levels. To mitigate these impacts, riparian buffer strips are maintained between harvested coupes and waterways. Retained vegetation slows overland flow during rainfall, allowing for infiltration and sediment deposition before reaching waterways.
Complicating the issue, buffer efficacy is influenced by landscape features that determine the infiltration capacity and water repellence of the soil and buffer quality (e.g. arid vs. wet environments). The implication of this is that some landscapes present a higher risk of sediment input into streams than others and different buffer widths are likely required to effectively mitigate this risk. Furthermore, riparian buffers include merchantable timber so while the under prescription of buffer widths can lead to negative ecological impacts, over prescription can lead to negative financial impacts to the industry; a balance must be found.
We conducted this project to better understand the effectiveness of buffer width prescriptions across south-east Australia. The overall aim of the project was to conduct a quantitative assessment of the effectiveness of buffers in limiting connection between eroding areas within timber harvesting units and streams through rainfall runoff simulations and hydrological modelling. We present the results here.