The Environment Agency has issued 26 severe flood warnings - its highest category - ahead of the most serious coastal tidal surge for over 60 years in England.

Communities along the North Sea coast from Northumberland down to the Thames Estuary and Kent, in addition to those on the Irish Sea coast from Cumbria down to Cheshire, could see significant coastal flooding later Thursday and into Friday. The coastline from Wells-next-the-Sea in Norfolk to Clacton, Essex, is particularly at risk, including Great Yarmouth and Lowestoft.

Storm surges present a very specific type of flood hazard to the east coast of England, mainly because of the semi-enclosed funnel shape, and the shallowness of the North Sea. For flooding to occur on open coastlines, an extra factor is needed to add to the height of the sea surface in addition to normal waves and tides, and severe meteorological conditions can provide this in the form of a sea surge.

In the devastating Big Flood of 1953 the disaster area stretched from Spurn Head in Yorkshire to the coast of Kent in the south.

The elevated water level moved along the coast with its crest starting at Spurn Head around 16.00 as it was getting dark, and reached a maximum height at King's Lynn at 19.20, about three-quarters of an hour ahead of high tide, before going down the East Anglia coast to reach Canvey Island at 01.10. No warning was issued, and on Canvey Island, homes were struck after the occupants had gone to bed.

What happened that night in the darkness was as sea defences and river banks were breached in places by the direct wave action, or overtopped and eroded by the surge sea walls were smashed by the wave action. In Suffolk and Essex, the sea surged up the estuaries overtopping and breaching river banks, inundating some coastal towns and villages from behind. Along the thousand miles of coastline, there were 1200 breaches of defences or flood penetration; in some places, no defences had been re-established since the war.

The flood struck the coastline with a sudden onset and without warning. Of the 307 deaths, at least 216 occurred in five main clusters: Mablethorpe and Sutton-on-Sea (16 dead), Hunstanton and Snettisham on the Wash (65 dead), Felixstowe and Harwich (over 40 dead), Jaywick (37 dead) and Canvey Island (58 dead).