The seasonal influence of large aquatic plants at contrasting study sites on the River Frome, Dorset

Watson, Kelly Joanne (2007) The seasonal influence of large aquatic plants at contrasting study sites on the River Frome, Dorset. PhD thesis, University of Nottingham.

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Abstract

This thesis utilised the River Frome, Dorset, as a study catchment within which to examine the seasonal effects of large aquatic plants, or 'macrophytes', on hydraulic roughness, water velocity, river stage and fine sediment distribution. The thesis formed part of LOCAR, a NERC thematic research programme, and was motivated by the need to provide empirical data to improve river management and to help achieve a compromise between vegetation management for flood control and for maintaining and maximising biodiversity.

The thesis employed a hierarchical research design with linked data collection at macro-, meso-, and microscales. (i) Macroscale research employed archival River Habitat Survey data and primary river surveys to place the more detailed meso- and microscale work in context. The analyses revealed the existence of a distinct chalk river group and examined the place of the River Frome within this. This provided contextual information to aid extrapolation of the current findings and facilitates comparisons with previous and future research. (ii) Mesoscale research focused upon stage and discharge measurements, and grid-based measurements of hydraulic variables. The analyses showed that macrophytes can have demonstrable and quantifiable effects on hydraulic roughness and sediment storage, which causes seasonal change in the stage/discharge relationship. However, this effect varies according to channel morphology and riparian land use and is subject to the attainment of a critical biomass. (iii) Microscale analyses employed high-frequency turbidity probes to investigate sediment processes within macrophyte beds. Each vegetation patch acted as a unique sediment filter, the characteristics of which changed over the growing season, and varied with distance along the patch. The results also suggested that retention of fine sediment is size selective and varies according to plant architecture and in-channel location.

The thesis findings imply that vegetation management must be approached with greater sensitivity to reach scale and sub-reach characteristics.

Item Type:Thesis (PhD)
Supervisors:Clifford, N.J.
Thorne, C.R.
Uncontrolled Keywords:River Frome, Dorset, macrophytes, hydraulic roughness, water velocity, river management, flood control, biodiversity
Faculties/Schools:UK Campuses > Faculty of Social Sciences, Law and Education > School of Geography
ID Code:2209
Deposited By:Ms. K EVANS
Deposited On:07 Oct 2011 10:21
Last Modified:07 Oct 2011 10:21

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