Metocean information for Channel Islands cable project

Supporting the design and installation planning of circa 100km of undersea cables

Guernsey Electricity Ltd and its partner, Réseau de Transport d’Électricité, are developing electrical links between Guernsey and France, and Guernsey and Jersey. To support the design and installation planning of circa 100km of cables, the project requires robust metocean information.

The bathymetry and current flow around Guernsey and the Channel Islands are highly complex and a bespoke modelling approach was required to adequately resolve local conditions and underpin the analysis tools.

A hydrodynamic hindcast model was built by extending ABPmer’s existing SEATATES tide and surge model to enhance the spatial resolution around the Channel Islands and along the Normandy coast of France. This nested approach allows us to retain the relatively wide model extents to the west of the North West European Continental Shelf which allow the development and propagation of storm events from the model boundaries through the model domain onto the continental shelf. Likewise, the representation of tidal dynamics has been found to be better simulated by allowing this wide model domain rather than a smaller ‘on-shelf’ boundary.

This bespoke local model was validated using local survey data. Using this approach a robust circa 40 year hydrodynamic hindcast was produced.

Metocean analyses were undertaken using the HD hindcast along with the 40 year wave hindcast from our SEASTATES wave hindcast model and publicly available wind data.

Outputs included characterisation of the metocean conditions, together with operational and extreme parameters along the routes.

Further analysis was provided as a weather downtime assessment which analysed the data for environmental thresholds and working weather windows, supporting the planning of construction activities.

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SEASTATES metocean information

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