Tide-surge interaction in the English Channel

Type Article
Date 2012
Language English
Author(s) Idier Deborah1, Dumas Franck2, Muller Heloise1
Affiliation(s) 1 : Bur Rech Geol & Minieres, F-45060 Orleans 02, France.
2 : IFREMER, Ctr Brest, F-29280 Plouzane, France.
Source Natural Hazards And Earth System Sciences (1561-8633) (Copernicus Gesellschaft Mbh), 2012 , Vol. 12 , N. 12 , P. 3709-3718
DOI 10.5194/nhess-12-3709-2012
WOS© Times Cited 49
Abstract The English Channel is characterised by strong tidal currents and a wide tidal range, such that their influence on surges is expected to be non-negligible. In order to better assess storm surges in this zone, tide-surge interactions are investigated. A preliminary data analysis on hourly surges indicates some preferential times of occurrence of large storm surges at rising tide, especially in Dunkerque. To examine this further, a numerical modelling approach is chosen, based on the 2DH shallow-water model (MARS). The surges are computed both with and without tide interaction. For the two selected events (the November 2007 North Sea and March 2008 Atlantic storms), it appears that the instantaneous tide-surge interaction is seen to be non-negligible in the eastern half of the English Channel, reaching values of 74 cm (i.e. 50% of the same event maximal storm surge) in the Dover Strait for the studied cases. This interaction decreases in westerly direction. In the risk-analysis community in France, extreme water levels have been determined assuming skew surges and tide as independent. The same hydrodynamic model is used to investigate this dependence in the English Channel. Simple computations are performed with the same meteorological forcing, while varying the tidal amplitude, and the skew surge differences D-SS are analysed. Skew surges appear to be tide-dependent, with negligible values of DSS (<0.05 m) over a large portion of the English Channel, although reaching several tens of centimetres in some locations (e. g. the Isle of Wight and Dover Strait).
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