Coastal sand dunes have been left unstable by tidal surges, leading to fears people may become trapped.
High waves lashed the north-east coast of England on Friday and overtopped sea walls.
Redcar RNLI said the dunes at Coatham in Redcar had "taken a battering" and rescuing people in sinking sand could be "very, very difficult".
Redcar Lifeboat operations manager Dave Cocks said the storm surge had left Coatham's dunes "very unstable".
"Once people have become trapped in sand it is a very, very difficult situation to be rescued from," he said.
The Friends of Redcar group has in the past highlighted the danger posed by shifting sands exposing the former landfill site.
Redcar councillor Carl Quartermain said Coatham dunes had now partly disappeared, revealing a "brick and masonry underbelly".
Redcar and Cleveland Council warned high tides could bring in debris along the coast following the tidal surge.
Elsewhere, a fisherman had to be rescued after being cut off by huge waves on Blyth Pier, while the pier at Saltburn had to be closed after it was damaged by the waves.
The River Tyne reached the top of temporary barriers on Newcastle and Gateshead quayside before the tide receded.