Storm surge computations in estuarine and near-coastal regions: the Mersey estuary and Irish Sea area

Jones, John Eric; Davies, Alan Marshall. 2009 Storm surge computations in estuarine and near-coastal regions: the Mersey estuary and Irish Sea area. Ocean Dynamics, 59 (6). 1061-1076. https://doi.org/10.1007/s10236-009-0228-z

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Abstract/Summary

An unstructured grid storm surge model of the west coast of Britain, incorporating a high-resolution representation of the Mersey estuary is used to examine storm surge dynamics in the region. The focus of the study is the major surge that occurred during the period 11-14 November 1977, which has been investigated previously using uniform grid finite difference models and a finite element model of the west coast of Britain. However, none of these models included the Mersey estuary. Comparison of solutions in the eastern Irish Sea with those computed with these earlier models showed that, away from the Liverpool Bay region, the inclusion of the Mersey estuary had little effect. However, at the entrance to the Mersey, its inclusion did influence the solution. By including a detailed representation of the Mersey estuary within the model, it was possible to conduct a detailed study of storm surge propagation in the Mersey, which had never previously been performed. This detailed study showed for the first time that the surge's temporal variability within the estuary is influenced by surge elevation at its entrance. This varies with time as a function of spatial and temporal variations of wind stress over the west coast of Britain. Within the Mersey, calculations show that the spatial variability is mainly determined by changes in bottom topography, which had not been included in earlier finite difference models. However, since water depth is influenced by variations in tidal elevation, this, together with tide surge interaction through bottom friction and momentum advection, influences the surge. The ability of the finite element model to vary the mesh in near-shore regions to such an extent that it can resolve the Mersey and hence the impact of the Mersey estuary upon the Liverpool Bay circulation shows that it has distinct advantages over earlier finite difference models. In the absence of detailed measurements within the Mersey at the time of the surge, it was not possible to validate predicted surge elevations within the Mersey. However, significant insight into physical processes influencing the surge propagation down the estuary, its reflection and spatial/temporal variability could be gained.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1007/s10236-009-0228-z
Programmes:	Oceans 2025 > Climate, ocean circulation and sea level Oceans 2025 > Shelf and coastal processes
ISSN:	1616-7341
Additional Keywords:	STORM SURGE; MERSEY ESTUARY; NEAR-SHORE REGION; FINITE ELEMENT MODEL; UNSTRUCTURED MESH GENERATION; WAVE-CURRENT INTERACTION; WIND-DRIVEN CIRCULATION; WEST-COAST; HYDRODYNAMIC MODELS; TIDAL RESIDUALS; SHELF; SENSITIVITY; TELEMAC; POLIRISH; MERSEY ESTUARY
NORA Subject Terms:	Marine Sciences
Date made live:	24 Jun 2010 11:26 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/9722

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