Identifying limitations of monitoring the success of river rehabilitation schemes for freshwater fish

Angelopoulos, Natalie Vivee

Abstract

Hydromorphological degradation impacts on habitat availability for biota in rivers. Degradation occurs as a consequence of multiple pressures driven by anthropogenic actions such as agriculture, urbanisation, industry, water supply, flood protection, navigation and transportation, fisheries and recreation. Rehabilitation of rivers is a tool that underpins the Water Framework Directive (WFD) by means of addressing river degradation by re-introducing habitat heterogeneity to impacted river systems. Many past and recent papers have highlighted a lack of information on the success of rehabilitation projects leading to a paucity of information and validation of the efficacy of such schemes. A review of 49 UK rehabilitation case studies found only 59% of these projects were monitored and worryingly only 24% of the 49 projects recorded any degree of success in the outcomes of the project. Clearly, there are limitations in monitoring the success of river rehabilitation schemes and it is this ‘key’ issue that is addressed in this thesis, to move from decisions based largely on subjective judgements to those supported by scientific evidence.

A literature review was carried out to identify best practise knowledge of the key steps for designing effective project planning for river rehabilitation and identifying existing limitations, focusing specifically on monitoring design and impact assessment. In addition to the literature review, a number of small scale rehabilitation case studies were monitored and evaluated to give a practical insight into the limitations and constraints that arise, when measuring projects success. Fish were selected as the chosen biological indicator and were monitored in addition to a number of habitat variables to identify rehabilitation success. The following array of case studies were evaluated, listed in order of complexity:

- Instream remediation of Driffield Beck, a small urban stream
- Channel narrowing of Lowthorpe Beck, a Yorkshire chalk stream
- Brash revetment to prevent bank erosion on the River Manifold
- Small weir removals on the River Dove
- Artificial riffle reinstatement on the River Stiffkey

As climate change pressures become more frequent on river systems, it also becomes an important driver for river rehabilitation mitigation and adaptation strategies. The EU Floods Directive and UK Flood and Water Management Act need to be integrated with the EU WFD and Habitats Directive, to work towards flood risk management (FRM) whilst still considering river heath. This approach is still in its early stages and there are no examples in the literature that report successful FRM that has incorporated river rehabilitation. Two case studies from an urban river setting on the River Don in Sheffield provide a practical insight into the limitations of monitoring and evaluating case studies where FRM is combined with river rehabilitation on the local habitat and fisheries.

Overall, monitoring was limited spatially and temporally for all case studies, this can be overcome by planning a suitable monitoring design before any rehabilitation takes place so long-term (pre and post), spatial monitoring can overcome natural variability. Furthermore, fish were a poor indicator for rehabilitation success over such a short monitoring timeframe; it is therefore advised that multiple biological quality elements are monitored to strengthen the evaluation of project success. Stocking of fish by the Environment Agency became a large hindrance when evaluating fisheries data for some of the case studies, because it masked changes that could have occurred as a result of rehabilitation. This is where the importance of communication between different stakeholders is vital, to reduce conflicting actions. Collaboration between FRM and conservation specialists is also necessary to achieve a win-win scenario and to endeavour to integrate these two conflicting objectives. There is much uncertainty when identifying rehabilitation success; current concepts in literature consider the application of endpoints and benchmarks against which to measure performance however, there are no definite criteria to date. Limitations, in monitoring and evaluating need to be overcome to establish appropriate targets for benchmarking and endpoints to reach project success. Furthermore, river restoration programme goals often only address problems on single rivers at a small scale and therefore have limited impact on catchment-scale processes. Potential benefits of implementing river rehabilitation and conservation at a catchment-scale are subsequently addressed.

Citation

Angelopoulos, N. V. (2013). Identifying limitations of monitoring the success of river rehabilitation schemes for freshwater fish. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4215218

• Thesis Type: Thesis
• Deposit Date: Feb 19, 2014
• Publicly Available Date: Feb 23, 2023
• Keywords: Biological sciences
• Public URL: https://hull-repository.worktribe.com/output/4215218
• Additional Information: Department of Biological Sciences, The University of Hull
• Award Date: Oct 1, 2013