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

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posted on 2020-07-30, 08:16 authored by Andrew Pledger, Matthew Johnson, Philip Brewin, John Phillips, Sarah L Martin, Dapeng YuDapeng Yu
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.

Funding

(EPSRC) Water Energy Food: Vaccinating the Nexus

History

School

  • Social Sciences

Department

  • Geography and Environment

Published in

Journal of Environmental Management

Volume

261

Publisher

Elsevier BV

Version

  • AM (Accepted Manuscript)

Rights holder

© Elsevier Ltd

Publisher statement

This paper was accepted for publication in the journal Journal of Environmental Management and the definitive published version is available at https://doi.org/10.1016/j.jenvman.2020.110259.

Acceptance date

2020-02-09

Publication date

2020-03-02

Copyright date

2020

ISSN

0301-4797

eISSN

1095-8630

Language

  • en

Depositor

Dr Andrew Pledger. Deposit date: 29 July 2020

Article number

110259

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