Storm surges caused by atmospheric forcing can be devastating, with long-lasting and diverse consequences. Historically, the UK has suffered major storm surges events, including in the Bristol Channel, which has the second largest tidal range in the world. In this paper, both statistical analysis and dynamic model studies were applied to investigate the potential conditions under which a large surge might occur in the Bristol Channel.
The Bristol Channel is an area of complex hydrodynamics which includes a very large tidal range, strong currents, extensive intertidal areas and river inputs, all of which contribute to frequent storm surges and flooding (Williams et al., 2012). For example, on the evening of 13th December 1981 a storm crossed southwest Britain, resulting in severe flooding in areas along the south side of the Bristol Channel from east of Bideford to near Gloucester (Proctor and Flather, 1989). This event produced a significantly high water level with return period as high as 102 years at Avonmouth, which is the highest return period event on record on that site (Haigh et al., 2015). Fig. 1 shows the variation of the water surface elevation of the 1981 storm surge event at Ilfracombe, the data was obtained from the British Oceanographic Data Centre (BODC) and refer to Admiralty Chart Datum (ACD). A good knowledge and understanding of such storm surges in the Channel is very helpful in assessing the associated risks that these events might present, both now and in the future.
This study first examined the occurrence and severity of storm surge events in the Bristol Channel over the period 1961-2015 by means of extreme values statistics using in situ data derived from tide gauges at five key locations along the east and west coasts of the Channel: Avonmouth, Newport, Hinkley Point, Mumbles and Ilfracombe (Fig. 2). Subsequently, a two-dimensional ADCIRC model whose domain includes Irish Sea, Celtic Sea, English Channel and Bristol Channel was built to investigate the influences of wind conditions on the storm surge events in the Bristol Channel.