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This program area will determine the effectiveness of conditions related to water quality. The program will do this by establishing an evidence base on how the riparian exclusion zones, riparian ground protection zones, road and track protocols and soil conditions adequately maintain water quality in Coastal IFOA state forests.
Monitoring waterway and wetland health
Monitoring plan - Waterway and wetland health
The program will determine if the Coastal IFOA conditions and protocols are effective in minimising the potential impacts of harvesting, roads, tracks and crossings on waterway and wetland health. It is important to understand the current state of knowledge in this area - including monitoring and research approaches - to ensure the program prioritises research and monitoring effort to address knowledge gaps and uncertainty.
Project WQ3: Monitoring class 1 drainage lines and exclusion zones
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- Research note - Stream buffers on NSW state forests (October 2024)
- Assessment report - Assessment of impact of class 1 drainage lines exclusion zone settings (May 2024)
As a part of the Coastal IFOA protocols, the monitoring program is required to evaluate the effectiveness of riparian protections for Class 1 streams, focusing on how well exclusion zone conditions around drainage lines prevent sediment from infiltrating the drainage systems.
Class 1 drainage lines, also known as ephemeral streams, are headwater flow paths found at the top of a catchment. Riparian buffers and exclusions zones are important for protecting water quality and habitat around these drainage lines. The exclusion zone conditions require a riparian buffer zone comprising both a ‘riparian exclusion zone’ and a ‘ground protection zone’, to be maintained around Class 1 drainage lines.
The project
We engaged Jacobs Group to assess the effectiveness of exclusion zone conditions for Class 1 drainage lines within the Coastal IFOA in minimising the impact of harvesting activities on waterways (assessment report above).
Jacobs aimed to answer two questions:
- Q1. Are the exclusion zone conditions (including both the riparian exclusion zone and ground protection zone) effective in minimising potential impacts on waterway condition? and
- Q2. Do ground protection zones perform as well as riparian exclusion zones (specifically those that have been accessed by machinery) in minimising the impact on waterway condition?
Jacobs designed and implemented a replicable field survey to evaluate the effectiveness of exclusion zones. The project was informed by multiple field visits and extensive collaboration with agencies, the Commission team, Dr. Peter Hairsine and peer reviewed by Prof. Jacky Croke from the Queensland University of Technology.
The findings
In regards to Q1, Jacobs modelled the worst case scenario where overland flow from snig tracks discharged directly into the buffers. In this instance, exclusion zones were most effective in situations where closer crossbank spacings (e.g. 10m apart) occur, in low to moderate rainfall and rainfall events intensities up to 1 in 10-year. They will be less effective where wider track crossbank spacings occur (e.g. greater than 30m apart) and in higher rainfall regions. The results were similar across the Coastal IFOA region, and not influenced by forest type or other environmental factors.
Regarding Q2, the ability to compare ground protection zones and riparian exclusion zones was limited by site availability, with no definitive conclusions able to be drawn at the regional level.
Jacobs advised a number of actions to improve exclusion zones including adopting a risk-based approach to ensure crossbank spacings are appropriate to manage relevant and local risks. After reviewing the report, the steering committee also agreed to develop a method toassess the risk of runoff generated on snig tracks in compartments potentially impacting instream water quality and habitat. The method should consider a range of factors including cross bank spacings, infiltration measures in the harvest area and riparian zone and rainfall intensity.
Project WQ1: Review of current knowledge for monitoring forestry impacts on waterway health
Project WQ1: Review of current knowledge for monitoring forestry impacts on waterway health
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Alluvium has delivered a peer-reviewed literature review on forestry impacts to waterway health and water quality in Coastal IFOA state forests. The review included research on practices and conditions in the Coastal IFOA. For example, temporary log crossings, class 1 stream riparian exclusion zones and soil and water protection in intensive harvest operations and exclusion zones for Coastal State Environmental Planning Policy wetlands.
The review found the management practices in the Coastal IFOA related to soil and water controls are consistent with best practice and standards. When major runoff events occur, the impact on water quality is typically short-term and transitory.
However, the frequency of intense rainfall and bushfires are likely to increase into the future due to predicted climate change. These predicted changes have the potential to increase the risk of impacts of timber harvesting on water quality in the future. As such, it is important that the objectives for this monitoring program reflect predicted changes in climate and monitoring is designed to investigate implication for the IFOA conditions and protocols.
Based on this review, the program will refine the objectives of the water quality monitoring plan to provide a stronger link between what is being monitored, and its relevance for values that are being managed for now and into the future. It will also adopt a risk based approach to monitoring. This approach will link timber harvesting, and the forest road network more broadly, to hydrologic and ecological impacts on waterways and wetlands. The approach will also measure catchment response in areas where harvesting and wildfire intersect. This will build a better understanding of how current forest management can be adapted to address emerging risk associated with new catchment disturbance regimes.
Project WQ2: Post-fire debris flow mapping in the Tumut and Tuross Catchments
Project WQ2: Post-fire debris flow mapping in the Tumut and Tuross Catchments
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Soils in eucalypt forests are at greater risk of erosion under high intensity rainfall conditions if vegetation cover has been impacted by disturbance events such as fire. Erosion events can increase sediment flows into waterways impacting water quality and aquatic habitat. However, the location and the volume of sediment transferred into waterways during these events is not well understood.
Following the 2019-20 wildfires, large rainfall events in 2020 provided an opportunity to advance our understanding of large episodic erosion events following fire. Further research about these events can provide options for improved forest management to protect waterway health. This is particularly important in the context of a predicted increase in the frequency of intense rainfall and bushfires due to climate change.
We engaged Jacobs to map post-fire debris flows (a form of sedimentation) in the fire-affected Tumut and Tuross catchments in southern NSW. Jacobs worked closely with the University of Melbourne and Forestry Corporation of NSW in delivering this work.
Jacobs used a model developed by the University of Melbourne (and previously used in Victoria) to assess and predict the impact of bushfire on sediment delivery into waterways. The project analysed new aerial imagery before and after the fires to measure channelised erosion in headwaters and debris flow occurrence. This is the first time that debris flows have been systematically mapped in NSW and linked to fire severity and other landscape features.
Jacobs found fire severity and terrain are key factors influencing the amount and frequency of debris flows. For instance, the frequency of debris flows increases under higher fire severity. Higher flows are also more associated with sedimentary and volcanic terrain than granite landscapes.
The report provides further discussion on plantations, agricultural land, the forest road network and areas to improve data generation and collaboration across institutions and jurisdictions.
Access to data used in the analysis is available on the TERN Data Discovery Portal.
Monitoring landscape-scale trends
Monitoring plan - Landscape-scale trends in environmental values
The Forest Monitoring Steering Committee commissioned the University of Melbourne to deliver baselines, drivers and trends for water quality and quantity in NSW forest catchments. The researchers have now delivered a final report which is available here.
