On 30 January 1607 ( New style ) thousands of people were drowned , houses and villages swept away , farmland inundated and flocks destroyed when a flood hit the shores of the Channel . The devastation was particularly bad on the Welsh side , from Laugharne in Carmarthenshire to above Chepstow on the English border . Cardiff was the most badly affected town . There remain plaques up to 8 ft ( 2.4 m ) above sea level to show how high the waters rose on the sides of the surviving churches . It was commemorated in a contemporary pamphlet " '' God 's warning to the people of England by the great overflowing of the waters or floods '' . " The cause of the flood is uncertain and disputed . It had long been believed that the floods were caused by a combination of meteorological extremes and tidal peaks , but research published in 2002 showed some evidence of a tsunami in the Channel . Although some evidence from the time describes events similar to a tsunami , there are also similarities to descriptions of the 1953 floods in East Anglia , which were caused by a storm surge . It has been shown that the tide and weather at the time were capable of generating such a surge
1953 floods in East Anglia
North Sea flood of 1953
Bristol Channel