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SEVERN BORE, THE GREAT FLOODS
In England, the storm surge is generally associated with the great east coast floods of 1947, when it was the turn of the Great Ouse to experience an exceptional tidal bore. However, old records show that numerous times the Bristol Channel experienced the effects of extreme depression and gale force winds. The Severn is prone to flood from Gloucester northwards in wet winters as ice thaws, and this was witnessed most recently in the winter of 2000. However, sometimes the threat comes from the ocean, producing a supertide and a giant tidal bore that devastate the countryside.
Courtesy Donny Wright
PHOTO PLATE INDEXSEVERN BORE PLATE 6
Here is a brief chronology of some of the greatest flood tides to have hit Severnside.

1483
John Paul, the former Vicar of Almondsbury, described briefly
'a wonderful flood and inundation in the river Severn which did unspeakable spoil as old records in Bristol report.'

January 20th 1606
The Great Flood.....Hundreds of people drowned between Minehead and Slimbridge as salt water to a depth of 2m swept across the land both sides of the estuary. Strong westerly gales blew in the channel, most likely the offshoot of an extreme depression off southern Ireland. John Paul described the incident thus...
'But the year 1606, the fourth of King James, the river of Severn rose upon a sodden Tuesday morning, the 20th January, being the full prime day and highest tide after the change of the moon, by reason of a mighty strong western wind. So that Minehead to Slimbridge the low grounds along the river Severn were, that turning tide, overflown, and in Saltmarsh many houses overthrown, sundry Christians drowned, hundreds of rudder cattle and horses perished, and thousands of sheep and lambs lost. Unspeakable was the spoils and losses on both sides of the river.'

1687, 1703, 1770
Great estuary floods are recorded by Atkyns (1712) and the Gentleman's Magazine (1773) but no detailed accounts of the events.

16th February 1957
The Supertide....The Citizen newspaper reported a 33'6" tide at Sharpness dock, which rose 5'4" at Gloucester flooding the Isle of Alney and washing over the carriageway at Minsterworth.

18th February 1995
The Supertide Returns!....A low depression and strong winds lead forecasts to predict a half metre surge on the tide. However, the wind swung westerly and jumped from force 3 to force 9 prior to the tide, forcing a revised prediction of a 1.3 metre surge. The Daily Telegraph, document a tidal bore four times its predicted height striking the Severn Estuary and parts of Gloucester. The A48 was closed and six thousand homes were without power for several hours.

While Chris Witts suggests that a major flood occurs on the Severn every 200 years as the result of excessive rainfall and ice thaw (Tales of the River Severn), the last two flood tides recorded above suggest the potential for a far more regular threat to the inhabitants of the estuary. Inherent in both dates is the meteonic nineteen year cycle of the moon. However this is purely a coincidence, since, while the tide of 1957 was the largest tide of the year, when the moon was at its closest possible passage to the earth, that of 1995 was in fact a rising spring, two months from the astronomical maximum tide. This tide was really the outcome of phenomenal winds in the channel and low pressure. Hence, the flood of 1995 should really be classified as a storm surge and not a supertide. Between them, these two tides do indicate the potential for damage if a supertide does coincide with extreme meterological conditions, as perhaps was the case in 1606.

Researched by Donny and Tom Wright

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