Storm Event

Overtopping and flooding in the south coast city of Portsmouth

Severity ? 2


The storm developed over southeast Canada on the 4th December 1994 and moved eastwards towards the UK. South of Iceland the storm turned and moved northwards. On the 6th of December the storm combined with, and was enhanced by, another low-pressure located to the west of Iceland. Central pressures deepened rapidly to about 940 mbars. The large depression then moved slowly westward and dissipated between Greenland and Iceland on the 9th December. In interaction with an anti-cyclone over southern Europe, the storm formed strong southerly to southwesterly winds over the British Isles.


The storm generated a skew surge of between 0.25 m and 0.75 m at many sites along the west, south and east coasts of the UK. Water levels exceeded the 1 in 5 year return level at one site, Portsmouth. Here the return period water level was 6 years. The corresponding skew surge was 0.68 m. The event occurred three day after peak spring tides.

Receptor and Consequence

The only coastal flooding known of for this event was in the south coast city of Portsmouth: two properties experienced minor flooding in Broad Street (Old Portsmouth) whilst waves overtopped a sea wall at Southsea which flooded the plant room of the Pyramids Leisure Centre PCC, 2008; PCC, 2009 – subsequently the sea wall was extended. If you know of any other incidents of coastal flooding during this event, and sources of information that describe it, please let us know.


Affected Sites

Name Return Period ? Water Level ? Tide ? Skew Surge ? Date ?
PORTSMOUTH 8 5.48 4.78 0.69 7th Dec 1994 02:00


  1. PCC (2008). Flooding in Portsmouth; list of flood incidents. Unpublished report provided by Portsmouth City Council. 
  2. Portsea Island Coastal Strategy Study – Strategy approval report. CPA Project Code: KY09. February 2009.: Portsmouth City Council. Available here. Accessed 28/04/2012.