Bathymetric evolution of the Mersey Estuary, UK, 1906–1997: causes and effects

Lane, Andrew. 2004 Bathymetric evolution of the Mersey Estuary, UK, 1906–1997: causes and effects. Estuarine, Coastal and Shelf Science, 59 (2). 249-263.

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There is increasing interest in quantifying bathymetric evolution of estuaries, specifically to determine past changes, monitor ongoing and ultimately predict future trends. The importance and urgency of this need arises from accelerating changes in mean sea level, growing evidence of climate change (influencing storminess and river flows) and changes in usages of estuaries. Analyses of existing long-term intensive observations in the Mersey indicate their value in addressing these issues. The Mersey is a macro-tidal estuary with extensive industrial and commercial activity, where long-term planning strategies are vital. The estuary has been widely studied because of its vital role in transport (in particular shipping), and the designation of parts of the inner estuary basin as nature reserves and ‘Sites of Special Scientific Interest’. Historically, the Mersey has been seriously polluted by industrial discharges and adjacent sea dumping. A comprehensive programme is presently being undertaken to improve water quality. The estuary has experienced a reduction of about 10% in volume over 70 years (Thomas et al., 2002), coupled with local sea level rise averaging 1.23 mm per year during the past century (Woodworth et al., 1999). Tidal propagation responds immediately and directly to changes in bathymetry and, to a lesser degree, to variations in bed-roughness determined by surficial sediments. Sediment transport patterns modulate this response providing a longer term balance. Asymmetries in the ebb and flow sediment fluxes adjust until an equilibrium state is restored (Friedrichs and Aubrey, 1988 and Dronkers, 1998). The first objective is to quantify the nature of the bathymetric evolution by using Empirical Orthogonal Function analysis of historical bathymetry observations (Section 3.1). In Section 3.2, observational evidence of accompanying tidal propagation changes in the estuary is examined. A 3-D hydrodynamic model is then utilised to examine whether these observed changes can be linked directly to the bathymetric evolution. Finally, in Section 5, the objective is to investigate whether the rates of bathymetric evolution are explained in terms of prevailing sediment budgets.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: POL Programmes
ISSN: 02727714
Additional Keywords: tides; elevations; currents; sediments; bathymetry; River Mersey
NORA Subject Terms: Marine Sciences
Date made live: 07 Jun 2013 13:23 +0 (UTC)

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