The Royal National Institution for the Preservation of Life from Shipwreck stationed a lifeboat at Portland in 1826, which was withdrawn in 1851. Coastal flooding has affected Portland's residents and transport for centuries—the only way off the island by land is along the causeway in the lee of Chesil Beach. At times of extreme floods (about every 10 years) this road link is cut by floods. The low-lying village of Chiswell used to flood on average every 5 years. Chesil Beach occasionally faces severe storms and massive waves, which have a fetch across the Atlantic Ocean. Following two severe flood events in the 1970s, Weymouth and Portland Borough Council and Wessex Water decided to investigate the structure of the beach, and coastal management schemes that could be built to protect Chiswell and the beach road. In the 1980s it was agreed that a scheme to provide storm protection with a 20% annual exceedance probability to reduce flood depth and duration in more severe storms. Hard engineering techniques were employed in the scheme, including a gabion running to the north of Chiswell, an extended sea wall in Chesil Cove, and a culvert running from inside the beach, underneath the beach road and into Portland Harbour, to divert flood water away from low-lying areas.