- 1st August 2022
- Posted by: Danielle Cosgrove
- Category: Projects
Location: Northumbria, UK Client: Northumbrian Water
We have recently worked with Northumbrian Water to carry out a series of investigations exploring the impact assets, such as reservoirs and catchwater structures, have on the ecology, hydromorphological processes and flow functionality of downstream watercourses. Our work provided Northumbrian Water with fifteen reports outlining the findings of our investigations and potential mitigation options.
Northumbrian Water possesses a number of assets, including catchwater structures and reservoirs, which are currently impacting the ecology, hydromorphological processes and flow functionality of the watercourses downstream. Consequently, Northumbrian Water is required to investigate options to mitigate the impacts of these assets and deliver demonstratable improvements under the Water Framework Directive (working towards Good Ecological Potential). Many of these assets are required to serve other key functions relating to water supply, flood risk, and power generation and so a need to balance these functions was critical.
The investigations involved:
· A review of existing information provided by the client
· Conducting an Initial Environmental Assessment (IEA) to identify the proximity of each site in relation to environmental designations and other environmental receptors
· Conducting combined fisheries and geomorphological walkover surveys to build an understanding of the geomorphological functioning and fish habitat in the watercourse
· Developing a flow record for the watercourse downstream of the assets. In some cases gauged data was used, in other cases, a flow record was estimated using a combination of overtopping flows and compensation flows
· Analysing the flow records to determine whether each of the UKTAG recommended ecological flow building blocks were being observed at the required magnitude and frequency
· Analysing fish densities to investigate fish community and population trends
· Analysing macroinvertebrate data metrics (LIFE, PSI and WHPT) to infer changes within macroinvertebrate communities which could be indicative of environmental pressures
· Conducting a geomorphological review which utilised elevation profiles, historic mapping, satellite imagery, and LIDAR together with observations from the geomorphological walkover surveys to understand the current geomorphological functioning within each system
Together these ecological, hydrological, and geomorphological investigations improved our understanding of the current whole-system functioning, enabling us to identify the key pressures within each system. This understanding informed the potential options identified, which were then assessed using multi-criteria analysis to evaluate the impact of each option on geomorphology, fisheries, cost, carbon and sustainability, water resources and flood risk.
Sites requiring a fish passage solution were further assessed using the EA Cost Benefit Tool to determine the Net Present Value (NPV) and Benefit Cost Ratio (BCR) of different fish passage options.
We provided Northumbrian Water with fifteen short, digestible reports which outlined the findings of our investigations and presented potential mitigation options. These options were assessed against multiple criteria and preferred options were identified. Recommendations were made detailing the next steps required to implement the proposed options. Recommended options for different sites encompassed in-channel habitat improvement works (including gravel augmentation and the introduction of localised woody debris), modifications to existing compensation releases (to ensure the flow regime meets UK TAG recommendations) and fish passage solutions (including structure removal and technical fish pass design).