14th century storms

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14th century storms

This article by retired Principal Meteorological Officer Frank Le Blancq was published in the 2011 Annual Bulletin of La Société Jersiaise.

For historians it is a fact of life that the further back in time we delve, in general the less direct evidence of events is available and the more we need to rely on secondary sources for evidence.

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In his note on the siting of St Brelade's Parish Church, Podger (2009) speculates that the storm of 23 November 1334 caused encroachment of the sea in St Ouen's Bay

Justification for this view is based on the work of Jean Poingdestre in 1695, who wrote that 'the sea has encroached during the last 350 years. Without knowing the contemporary documents to which he refers, I take this to be an approximate span of time and it may be a coincidence that the dates are 351 years apart. If an exact date were known to him, why did Poingdestre not use it? We should also note that Poingdestre mentioned the Parish of St Ouen, where the coast faces south-west.

There can be no doubt that a severe storm occurred on 23 November 1334. Known as the St Clemens flood, it caused thousands of deaths along the Dutch and Flemish coasts as the sea broke through protective dykes. A piece of evidence from England can be found in research into maritime flooding and storm events in the Thames Estuary from 1250 to 1450 (National Maritime Museum), which notes the vulnerability of marshland around the mouth of the Medway in north Kent.

The research cites manuscript accounts for the manor of Barksore, which catalogues a major breach in the sea wall in the winter of 1334-35, almost certainly caused by this storm. For such a breach to occur in north Kent, the most likely meteorological situation is a deep depression in the North Sea with a north-west or northerly storm driving a tidal surge down the east coast of England into the Thames Estuary, similar to the devastating flood event of 31 January 1953.

A south-west or westerly storm would blow water out of the Thames Estuary, not into it, and it is therefore unlikely to result in a breach of sea defences. The late Professor Lamb was a noted expert on historical storms in north-west Europe. Using his analysis of the 1943 storm as an analogue, such a storm would result in a west to north-west wind over the Channel Islands, leading to the conclusion that the 1334 storm was unlikely to have caused an inundation of St Ouen's Bay. The bay is more vulnerable to south-westerly storms.

1883 review

In a review of evidence of flooding in St Ouen's Bay, Le Cornu (1883) makes mention of the 'ancient document' published in the 1849 Almanach de la Chronique, which states that the sea inundated part of St Ouen in 1356 and is said to have destroyed the Foret de la Brecquette. Unfortunately there is no record of a severe storm in 1356, so can we rely on 1356 as an exact year for the storm? If not, are there alternative dates in the mid-14th century>

According to Britton (1937) the remarkable storm of 15 January 1362 is probaby the severest storm in our records, with the exception of that of 26 November 1703. Half a century later Rowe (1988) came to the same tentative conclusion after comparing three severe historic storms with that of 15/16 October 1987.

In England the 1362 storm was known by its date as St Maury's Wind, but on the Continent is referred to as the Grote Mandrenke (great drowner of men) due to the heavy loss of life along North Sea coasts. Numerous accounts of the effects of this storm exist, with extensive damage reported over southern England. Britton quotes a contemporary report by John of Reading, who wrote of the 'west or south wind called Africus' and how there 'hardly remained entire a house or tree in its course'.

Other contemporary reports write of a great wind out of the south-west, the most likely direction to result in inundation in St Ouen's Bay and particularly the parish of St Ouen, where the coast faces south-west. By implication we can include the Channel Islands within the swathe of severe winds, using the storms of November 1703 and October 1987 as analogues.

There is strong secondary evidence to suggest that St Ouen's Bay was subject to an inundation in the mid-14th century, but I would contend evidence is not strong enough to categorically state which storm was the cause. Meteorologically I suggest St Maury's Wind in 1362 is the more likely contender; it is close to the year 1356 and falls within Poingdestre's 350 years. However, we cannot exclude 1334 from the reckoning, for it could have initiated erosion which aided an inundation of St Ouen's Bay in 1362.

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