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A strategic programme for NERC Lowland catchment research
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Vegetation influences on fine sediment transport


Vegetation influences on fine sediment and propagule dynamics in groundwater-fed rivers: implications for river management, restoration and riparian biodiversity

Overview of project

The project investigated interactions between flow hydraulics, sand and finer sediment and vegetation along three river reaches - two on the River Frome in Dorset and one on the River Tern in Shropshire. The study reaches were bordered by essentially unmanaged riparian vegetation. The project established that aquatic and riparian vegetation interacts with river flows to accelerate sedimentation. This interaction is particularly strong at the base of river banks colonised by emergent macrophytes (plants visible to the naked eye). The river-transported sediment contains large numbers of diverse seeds, including numerous wetland and terrestrial species which can germinate in aggrading sediments. This process demonstrates a crucial link between vegetation, river channel form and bank stability that also underpins riparian habitat diversity and turnover, and vegetation diversity along the study reaches. In short, vegetation along unmanaged river margins, engineers channel margin form and vegetation species diversity. This natural process needs to be recognised in the management and conservation of lowland groundwater-fed rivers.


  • To investigate interactions between vegetation, river flows, and sediment/vegetation propagule dynamics in groundwater-fed rivers and develop a classification of groundwater river reaches.
  • To integrate observations of flow, fine sediment and propagule transfer processes with vegetation biomass and channel morphology dynamics in river reaches, through the assessment of the hydraulic signature of different reach types and the application of ordination techniques to the ecological and sedimentological data.
  • To give insights into the impact of vegetation on sediment and propagule dynamics and support the development of management guidelines.

Main findings

  • Previous research has highlighted the importance of buoyancy for seed dispersal by water, but the research conducted during this project demonstrated that the river bed is a significant store of viable seeds which can be mobilised and redeposited on the river banks during floods.
  • High river flows were far more important than local seed fall for depositing seeds across the river banks
  • 44% of deposited seed species were not present in the vegetation and the largest proportions were deposited in winter, following river transport into the study reaches from upstream areas.
  • The quantity and species richness of seeds deposited on the river bank was very strongly related to the quantity of finer sediment deposited, demonstrating a direct link between seed deposition and hydraulic conditions during inundation.
  • A crucial influence on sediment and seed deposition was the amount and rigidity of vegetation.
  • Particular types and patches of vegetation are so effective at trapping seeds and sediments that they engineer landform development and reinforcement and plant successions.

Areas of application

The development of cost effective approaches to river restoration, including vegetation planting to induce channel narrowing, increased sinuosity, increased habitat complexity. Such measures would assist in achieving good ecological status under the Water Framework Directive.

Researchers' details

Principal Investigator:


Other researchers:

  • P Armitage, Centre for Ecology and Hydrology
  • J Goodson, Entec UK
  • G Harvey, University of Nottingham
  • H Moggridge, King's College London
  • K Thompson, University of Sheffield.


All publications from this and other LOCAR projects are listed in the publications database.

Refereed journal papers

Clifford, N.J., Skinner, K. 2005. River restoration: an overview of approaches from a habitat and geomorphological perspective. In: Pierson, G. (ed.), Proceedings of the 34th Annual Study Course, 2003. Institute of Fisheries Management. 79-97.

Clifford, N. J., Harmar, O. P., Harvey, G. and Petts, G. E. 2006 Physical habitat, eco-hydraulics and river design: a review and re-evaluation of some popular concepts and methods, Aquatic Conservation, Marine and Freshwater Science, 16, 389-408.

Corenblit, D., Tabacchi, E., Steiger, J., Gurnell, A. 2007. Reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics: a review of complementary approaches. Earth Science Reviews, 84, 56–86

Gurnell, A.M. 2007. Analogies between the dynamics of mineral sediments and vegetative particles in fluvial systems. Geomorphology, 89, 9-22.

Gurnell, A.M., Thompson, K., Goodson, J., Moggridge, H. 2008. Propagule deposition along river margins: linking hydrology and ecology. Journal of Ecology, 96, 553-565.

Gurnell, A.M., Goodson, J., Thompson, K., Clifford, N., Armitage, P. 2007. The river bed: a dynamic store for viable plant propagules? Earth Surface Processes and Landforms, 32, 1257–1272.

Gurnell, A.M., Goodson, J., Thompson, K., Mountford, J.O., Clifford, N. 2007. Three seedling emergence methods: implications for interpretation of propagule deposition in riparian zones. Seed Science Research, 17, 183-199.

Gurnell, A.M., Tockner, K., Petts, G.E., Edwards, P.J. 2005. Effects of deposited wood on biocomplexity of river corridors.. Frontiers in Ecology and Environment, 3, 377-382.

Gurnell, A.M., van Oosterhout, M.P., de Vlieger, B., Goodson, J.M. 2006. Reach-scale impacts of aquatic plant growth on physical habitat, River Research and Applications, 22, 667-680.

Harvey, G., Clifford, N.J. and Gurnell, A.M. 2007. Towards an ecologically meaningful classification of the flow biotope for river inventory, rehabilitation, design and appraisal purposes. Journal of Environmental Management available on-line.

PhD theses

Moggridge, H. 2007. The dispersal, establishment and growth of vegetation in riparian zones. PhD Thesis, King’s College London

Watson, K. 2006. The seasonal influence of large aquatic plants at contrasting study sites on the River Frome, Dorset. PhD Thesis, University of Nottingham.

Harvey, G. 2006. Characterising river habitat at the reach scale, River Tern, Shropshire. PhD Thesis, University of Nottingham.

Bachelor’s thesis

M.P. van Oosterhout and B. de Vlieger 2004. An appraisal of the influence of Ranunculus penicillatus spp. pseudofluitans on hydraulics and river bed material under different morphological and shading circumstances in the River Frome. Unpublished Batchelors Dissertation, Larenstein University (work undertaken at King’s College London, supervised by A.M. Gurnell).

Recommended reading

Boitsidis, A.J., Gurnell, A.M., Scott, M., Petts, G.E., Armitage, P. A 2006. Decision support system for identifying the habitat quality and rehabilitation potential of urban rivers. Water and Environment Journal, 20, 1-11.

Bombino, G., Gurnell, A.M., Tamburino, V., Zema, D., Zimbone, S.M. 2007. A method for assessing channelization effects on riparian vegetation in a mediterranean environment. River Research and Applications 23: 613–630

Gurnell, A.M., Boitsidis, A.J., Thompson, K. and Clifford, N.J. 2006. Seed bank, seed dispersal and vegetation cover: Colonisation along a newly-created river channel. Journal of Vegetation Science, 17, 665-674.

Gurnell, A.M., Lee, M., Souch, C. 2007. Urban rivers: Hydrology, Geomorphology, Ecology and Opportunities for Change. Geography Compass 1, 1118–1137

Gurnell, AM, Morrissey, IP, Boitsidis, AJ, Bark, A., Clifford, NJ, Petts, GE, Thompson, K. 2006. Initial Adjustments within a New River Channel: Interactions between Fluvial Processes, Colonising Vegetation and Bank Profile Development. Environmental Management 38, 580-596. ISBN 0364-152X, Doi 10.1007/s00267-005-0190-6

Gurnell, A.M., Petts, G.E. 2006. Trees as riparian engineers: the Tagliamento River, Italy. Earth Surface Processes and Landforms. 31, 1558-1574.

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