Kenneth Pye Associates Ltd.
 Scientific Research, Consultancy and Investigations

              
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Morpological changes and their causes in Essex estuaries
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The conservation of estuarine habitats requires a detailed understanding of the processes operating and morphological response to both environmental forcing factors and anthropogenic influences.  In addition, commercial and recreational activities within estuaries, as well as the flood protection of adjacent low-lying agricultural land, could be affected by morphological change in estuaries.

This study focused on recent trends in four Essex estuaries, namely the Colne, Blackwater, Roach and Crouch.  Sedimentation trends during the period 1993 to 2001 were assessed using bathymetric and topographic surveys commissioned by the Environment Agency.  Sediment volume changes were calculated for selected profile lines along the length of each estuary.  Various factors affecting estuary morphology were then investigated, including changes in sediment supply, saltmarsh erosion/accretion, tidal levels, currents, wind/wave activity, dredging regime and navigation practices.

Cross-section of the River Crouch near Burnham-on-Crouch in 1997.

Volume change between highest and lowest astronomical tides in the Blackwater Estuary between 1993 and 2001.

Wave rose for all waves in 2000 at Kentish Knock.

Annual percentage of waves from all directions greater than 2.0 m and 2.5 m in height at Kentish Knock

Results showed that the Colne, Roach and Crouch estuaries experienced net accretion over the period 1993 to 2001.  It is postulated that several inter-related factors have contributed to this sedimentation:

1. Increased freshwater discharge and fluvial sediment supply due to higher rainfall
2. Changes in salinity regime and turbidity maximum behaviour
3. Reduction in the frequency of larger waves from the south-east quadrant

All these changes are related to a greater dominance of westerly 'depression' type weather over the south-eastern part of the British Isles.

Publications and Reports

Saye, S.E., Blott, S.J. and Pye, K. (2003). Morphological and bathymetric changes and their causes in Essex estuaries. Kenneth Pye Associates Ltd., Internal Research Report IR002, 175 pp.

van der Wal, D. and Pye, K. (2000). Long-term morphological change in the Blackwater Estuary, southeast England. SPME, Royal Holloway, University of London, Research Report CS6, 34 pp.  

Kenneth Pye Associates Ltd. - Environmental Consultants
Page last modified: October 03, 2007