Two great new online resources for NRM Practitioners and Land Managers
Mar 31, 2015
Two great new CSIRO publications that were recently published online. These reports describe the drivers and processes of gully and bank erosion in the GBR catchments, spatial priorities for remediation and the cost-effectiveness of remediation options. System level issues such as prioritising remediation (e.g. protect intact areas first), treating both the drivers and symptoms of erosion (e.g. managing runoff) and the importance of monitoring and evaluation are also discussed. Recommendations are made for designing programs that effectively manage gully and bank erosion in catchments draining to the Great Barrier Reef. These reports were funded by the Australian Government (Reef Program).
Gully erosion is an important contributor to sediments and nutrients entering the GBR lagoon. Gullies that formed up to 140 years ago are today continuing to expand, delivering an unacceptably high level of sediment and nutrient to the lagoon of the Great Barrier Reef. This report reviews recent sediment source tracing, erosion mapping and catchment modelling studies, finding that gully erosion contributes approximately 40% of all fine sediment to the GBR lagoon. This makes gully management a high priority for investments to reduce sediment loads. The report concludes by providing recommendations to implement targeted and comprehensive gully control techniques, to refocus plans for improving the water quality in the Great Barrier Reef lagoon.
This report synthesises available information on the spatial locations, causes and control measures of gully erosion in GBR grazing lands. It proposes an efficient and evidence based approach to reducing the loads of fine sediment and associated nutrients to the GBR lagoon, which involves targeting erosion management to gullies within the management units that deliver fine sediment most efficiently to the GBR lagoon. A combination of low technology revegetation techniques is recommended to be implemented by or in partnership with land managers, including fencing, seeding and small sediment trapping structures. While gully erosion in grazing lands has previously been recognised as key a factor influencing water quality, the proposed approach is a significant change in the focus of land-based activities to improve water quality.
Stream bank erosion, which is one of three processes representing sub-surface erosion, is estimated to contribute ~30-40% to end of catchment sediment yields. Stream bank erosion, meander migration and lateral channel change are terms used to describe the erosion of the channel boundary in river systems. However, our understanding of the degree of alteration of bank erosion with the introduction of agriculture, and the success of methods for remediating bank erosion sites, is limited. Without a robust understanding of these issues it is difficult to target the sites for remediation as well as to evaluate the costs and benefits of undertaking remediation.
This report had five key objectives. Firstly, to review the International literature and identify the key processes driving stream bank erosion. It is considered important to understand the drivers, and not just the symptoms, of stream bank erosion. Secondly, using the SourceCatchment model, which incorporates the key processes driving stream bank erosion, identify the relative risk of stream bank erosion in each of the 47 GBR management units. Thirdly, to discuss some of the issues that should be taken into consideration prior to remediation. These include the available options, effectiveness, time lags, and monitoring and evaluation needs of the remediation. Fourthly, to discuss the potential cost of the remediation, as well as the various options for delivering the funding. Finally, this information is demonstrated on two case study catchments, the Burdekin and Daintree basins.
Check them out to find out more!