The North Sea flood of 1953, also known as the Big Flood or East Coast Flood or as the Flood Disaster, was a flood caused by a heavy storm surge in the North Sea that struck low-lying coastal areas of the Netherlands, Belgium, and the United Kingdom. More than 2,000 people were killed on land and hundreds more at sea. It was the worst natural disaster of the 20th century in the United Kingdom and the worst in the Netherlands since the Middle Ages.