At a global scale, many rivers have been degraded by anthropogenic activities, including agriculture, sewage discharge and chemical contaminations. Growing awareness of river degradation, coupled with climate change and an increase in flooding has led to a recent surge in river restoration projects. Across the UK and the globe many other countries), river restoration projects have transitioned away from conventional engineering approaches to working with a river’s natural processes. These methods include Natural Flood Management (NFM) which often uses wood structures to slow the flow of water, helping to reduce flood risk whilst delivering a range of multiple environmental benefits. Natural Flood Management Wood Structures (NFMWSs) also have several secondary effects, including affecting biogeochemical processes and influencing particulate organic matter (POM) retention. Much of the previous research on NFMWSs has focused on their geomorphic (e.g. formation of pools, sediment storage, bank erosion) and ecological (e.g. macroinvertebrates, fish) effects on the river system. However, few studies have characterised the effect of NFMWSs on seasonal changes in water quality, including the presence of nutrients, specifically phosphates, nitrates, minerals, metals, total suspended solids in the water column and also POM. This research also aims to examines the effect of NFMWSs, immediately upstream and downstream the gap between the log and the stream bed and how the number of logs influence on water quality and POM. The results are compared with the control stream, and the water quality of agricultural streams and the main stream, Crimsworth Dean Beck. Since 2018, Slow The Flow, in partnership with the National Trust have installed over 1000 NFMWSs in the upper Hebden Water catchment, at Hardcastle Crags, in West Yorkshire, in the UK. The NFMWSs varied in design, structure, and dimensions. Fieldwork was undertaken across eight headwater streams within Crimsworth Dean Wood, within the upper Hebden Water catchment, in Winter 2022 (water quality) and Spring 2023 (seasonal variation in water quality and POM analysis).Seasonal comparisons revealed changes in water quality between Winter 2022 and Spring 2023 across NFMWS sites. Winter showed statistically significant elevated nitrate concentrations whilst Spring had significantly higher phosphate concentrations and sediment phosphorus levels. Velocity, total suspended solids, and metal concentrations also varied, although they either contradict the alternative hypotheses, or were not statistically significant. Analysis of POM content revealed that NFMWSs sites had a higher POM content and a higher proportion of fine particle sizes, 0.212mm or below, compared to the control stream, supporting the alternative hypotheses. Whilst NFMWSs did not have a significantly higher POM depth compared to the control stream, which contradicts the alternative hypothesis. However, the output of the Linear-mix model did support that higher POM content is driven by greater POM depths. Overall, the findings of this study demonstrate that NFMWSs have an effect on water nutrients and POM retention. Beyond the academic research output, this research supports a wider effort to shape government policy on NFM, and strengthen the work already being achieved by environmental charities such as Slow The Flow, by influencing the legislators. This study supports with scientific evidence the outcome of community action and hopefully supports further collaboration between researchers, practitioners. For example, the importance how log placement and structure and can have a subsequent impact on the influencing nutrient cycling, sediment dynamics and POM. Although, future studies should examine the impact NFMWSs have on a catchment scale. By taking these approaches, it will help advance our understanding of NFMWSs effectiveness under different environmental, informing best practice and guiding future policy development for sustainable river catchment management.
| Date of Award | 16 Dec 2025 |
|---|
| Original language | English |
|---|
| Sponsors | Slow The Flow |
|---|
| Supervisor | Ryan Wilson (Main Supervisor) |
|---|