Characterising the geomorphological and physicochemical effects of water injection dredging on estuarine systems

Pledger, Andrew; Johnson, Matthew; Brewin, Philip; Phillips, John; Martin, Sarah; Yu, Dapeng

Abstract

Dredging is a globally important aquatic system management activity, used for navigation improvement, contamination removal, aggregate production and/or flood risk mitigation. Despite widespread application, understanding of the environmental effects of some dredging types remains limited. Field campaigns in 2016 and 2017 in the River Parrett estuary, UK, therefore investigated the geomorphic and physicochemical effects of Water Injection Dredging (WID), a poorly studied hydrodynamic dredging technology. WID, applied to restore channel capacity for the maintenance of flood water conveyance in the tidal River Parrett, influenced surface elevations but not grain-size characteristics of dredged bed sediments. Topographic alterations due to the 2016 WID operation were short-lived, lasting less than 10 months, although benefits of the 2017 WID operation, in terms of volumetric change, outlasted the ? 12-month study period. Dredging had a significant impact on water physicochemistry (pH, dissolved oxygen, total suspended solids and turbidity) when comparing pre- and during- dredging conditions within the dredge reach, although time-series analysis found dredging effects were comparable in magnitude to tidal effects for some parameters. WID is typically targeted at the thalweg and not the banks, rendering the geomorphic signature of the method different to those of other, often more invasive dredging technologies (e.g. mechanical dredging methods). Further, thalweg not bankside dredging may have potential positive ecological implications, particularly where the majority of biomass is located within the channel margins, as in the tidal River Parrett. Collectively, data suggest WID can be an effective method for sediment dispersal within tidal systems although regular application may be required to maintain cross sectional areas, particularly where management precedes periods of low flows and/or high rates of sediment accumulation. In future, more work is required to better understand both the physical and ecological implications of WID as a flood risk management tool in estuaries and rivers.

Citation

Pledger, A., Johnson, M., Brewin, P., Phillips, J., Martin, S., & Yu, D. (2020). Characterising the geomorphological and physicochemical effects of water injection dredging on estuarine systems. Journal of Environmental Management, 261, https://doi.org/10.1016/j.jenvman.2020.110259

• Journal Article Type: Article
• Acceptance Date: Feb 9, 2020
• Online Publication Date: Mar 2, 2020
• Publication Date: May 1, 2020
• Deposit Date: Feb 11, 2020
• Publicly Available Date: Mar 3, 2021
• Journal: Journal of Environmental Management
• Print ISSN: 0301-4797
• Electronic ISSN: 1095-8630
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 261
• Article Number: 110259
• DOI: https://doi.org/10.1016/j.jenvman.2020.110259
• Keywords: Environmental Engineering; Waste Management and Disposal; Management, Monitoring, Policy and Law; General Medicine
• Public URL: https://nottingham-repository.worktribe.com/output/3946268
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0301479720301948
• Additional Information: This article is maintained by: Elsevier; Article Title: Characterising the geomorphological and physicochemical effects of water injection dredging on estuarine systems; Journal Title: Journal of Environmental Management; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.jenvman.2020.110259; Content Type: article; Copyright: © 2020 Elsevier Ltd. All rights reserved.