In years past, the Dutch coastline has changed considerably as a result of human intervention and natural disasters. Most notable in terms of land loss is the 1134 storm, which created the archipelago of Zeeland in the south west. The St. Elizabeth flood of 1421 and the mismanagement in its aftermath destroyed a newly reclaimed polder, replacing it with the 72 square kilometres (28 sq mi) Biesbosch tidal floodplains in the south-centre. The most recent parts of Zeeland were flooded during the North Sea Flood of 1953 when 1,836 people were killed, after which the Delta Plan was executed. The disasters were partially increased in severity through human influence. People had drained relatively high lying swampland to use it as farmland. This drainage caused the fertile peat to compress and the ground level to drop, locking the land users in a vicious circle whereby they would lower the water level to compensate for the drop in ground level, causing the underlying peat to compress even more. The problem remains unsolvable to this day. Also, up until the 19th century peat was mined, dried, and used for fuel, further adding to the problem.