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Chris Checkley (2011)

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Citation An impressive, modeling-based dissertation focussed on wave and tidal modeling in the Scilly Isles, with clear aims and excellent standard of presentation.

Title: An Evaluation of Wave Conditions and Coastal Features around the Isles of Scilly utilising: Wave Refraction Modelling and Coastal System Mapping

A wave prediction model was implemented and tested in the Scillonian Archipelago, based on the state of the art spectral phase averaging model, SWAN. The model analysed the effect of swell waves on the near shore environments of the Isles of Scilly. Observed wave data from the Sevenstones Light Vessel was used to force two contrasting wave conditions, representative of the period 2003-2008. Two levels of SWAN simulation were successively linked through nested model runs and the influence of varying tidal levels was evaluated.

Analysis determined the relative importance of bathymetry, tidal condition and forced wave condition on the wave regime. The raised platform on which the Isles of Scilly sit dissipated large amounts of wave energy. As a consequence, minimal wave energy was dissipated near the coastlines of the larger islands. The only exceptions were islands located adjacent to the boundary of the raised platform. The detailed bathymetry of the platform, characterised by sounds and passages, controlled wave vectors. Storm wave conditions increased wave energy along the exterior coastlines of islands but increases were not uniform and interior coastal areas experienced
negligible changes. Variations in tidal condition significantly altered ocean surface topography around the Isles, shifting wave vectors and modifying significant wave heights.

An evaluation of the effects of the newly incorporated phase decoupled approach for diffraction in SWAN was undertaken. Differences in wave vectors and heights were observed, however, diffraction significantly increased computational times and created notable instability within model outputs.

Coastal System Mapping of a sample area qualitatively validated model results. Coastal System Mapping of the entire archipelago would be highly beneficial. The use of software such as Cmap Tools would create a repository for past data and research; a framework for large scale synthesized understanding of the links between the coastal environment and the wave regime.

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