St. Lucia's flood (Sint-Luciavloed) was a storm tide that affected the Netherlands and Northern Germany on December 14, 1287 (the day after St. Lucia Day) when a dike broke during a storm, killing approximately 50,000 to 80,000 people in the fifth largest flood in recorded history. Much land was permanently flooded in what is now the Waddenzee and IJsselmeer. It especially affected the north of the Netherlands, particularly Friesland. The city of Griend was almost destroyed, only ten houses were left standing. The name Zuiderzee dates from this event, as the water had merely been a shallow inland lake when the first dikes were being built, but rising North Sea levels created the "Southern Sea" when floods including this flood came in.
Although not known by the name of St Lucia, the same storm also had devastating effects on the other side of North Sea in England. The city of Winchelsea on Romney Marsh was destroyed (later rebuilt on higher ground). Nearby Broomhill was also destroyed. The course of the nearby river Rother was diverted away from New Romney, which was almost destroyed and left a mile from the coast, ending its role as a port. The Rother ran instead to sea at Rye, prompting its rise as a port. The storm contributed to the collapse of a cliff at Hastings, taking part of Hastings Castle with it, blocking the harbour and ending its role as a trade centre, though it continued as a centre for fishing. Parts of Norfolk were flooded, eg the village of Hickling where 180 died and the water rose a foot above the high altar in the church. The port of Dunwich in Suffolk began its decline. Whitstable in Kent is also reported to have been hit by the surge.
In all, the storm can be seen to have had a powerful effect on the Cinque Ports, two of which were hit (Hastings and New Romney), along with the supporting "Antient Town" of Winchelsea. Meanwhile, the other Ancient Town of Rye was given a leg up.