National Network of Regional Coastal Monitoring Programmes

Introduction

The storm catalogue is an archive of the spatial footprint and associated storm track of extreme wave events (defined by the 1 year return period Hs) captured by the wave buoy network operated by the National Network of Regional Coastal Monitoring Programmes of England since 2003. It is the result of an effort by the Channel Coastal Observatory to synthesise the wave data collected by the network, and is updated on a continuous basis. Although the rationale behind the location of each buoy is to provide site-specific wave information, the number of buoys currently deployed means that they can produce a consistent, spatially-representative, shallow water wave climate of the English coast.

The catalogue is organised so that the user can browse extreme wave events either by storm season or by the region that was impacted by a storm. There are two maps for each storm; one showing the spatial footprint of the event and the other the associated storm track. There is also a table showing the peak wave heights and return periods at each site, together with the tidal stage at the peak of the storm.

The method of extremes analysis that underpins the storm catalogue is described in TN03, available from http://www.channelcoast.org/reports/
Dhoop, T. & Thompson, C. 2018. Extreme Value Analysis for CCO Coastal Wave Data. Channel Coastal Observatory TN03.

Full details of the background can be found in the open access peer-reviewed paper:
Dhoop, T. & Mason, T. 2018. Spatial Characteristics and Duration of Extreme Wave Events around the English Coastline. Journal of Marine Science and Engineering. 6(1), 14; DOI: 10.3390/jmse6010014 http://www.mdpi.com/2077-1312/6/1/14. Each of the events described in the paper are documented in this spreadsheet.

The images in this catalogue are free to use under the Open Government Licence using the following copyright and acknowledgement:
Copyright: New Forest District Council
Acknowledgement: Image courtesy of the National Network of Regional Coastal Monitoring Programmes

Reading the Maps

The storm footprint maps display wave height return periods achieved at each wave buoy (indicated by circle size) and the timing of peak wave height relative to High Water (indicated by circle colour). Sites where data were recorded but the storm threshold was not exceeded are plotted in blue. Each storm event is also contextualised by a tidal coefficient – a number between 20 (very low neap tide) and 120 (very high spring tide).

Tidal Coefficient

The tidal coefficient represents the tidal amplitude using a number between 20 (very low neap tide) and 120 (very high spring tide). The system used in this storm catalogue is adapted from the system developed at SHOM, the French Naval Hydrographic and Oceanographic Service, and widely used in France.

The tidal coefficient is calculated using the formula:

Ct = 20 + 100 x [(Rt - Rmin) / (Rmax - Rmin)]

where Rt is the maximum tidal range on a given day (the storm peak), and Rmin and Rmax are the minimum daily tidal range and maximum daily tidal range, respectively, from a 40-year time series of tidal predictions. For the purposes of the storm catalogue, the tidal coefficient is calculated at Herne Bay.

The tidal coefficient is described using the ranges in the table below:

Regional Partitioning

The English coastline has been partitioned into sections of coast which have a distinct and common behavioural response to extreme wave events.

Acknowledgements

Wave data are measured at NNRCMP wave buoy sites together with two industry-owned buoys (Rhyl Flats and Gwynt Y Mor from RWE Innogy Ltd.), while tide data are predictions at NNRCMP and NTSLF tide gauge sites.

The tidal coefficient method was adapted from the method developed at SHOM, the French Naval Hydrographic and Oceanographic Service.