Efforts to protect a section of coastline near Sidmouth have been hampered by recent stormy weather.
Cliffs at Pennington Point were to be shored up with shingle dredged from the River Sid.
But the shingle, left on the beach prior to being moved, has been washed away by high tides and bad weather.
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The man who carried out the Westminster attack is thought to be British born and was once investigated by MI5, the Prime Minister has said.
More than 50 primary school children from Somerset, who were caught up in the terror attack in Westminster, have returned home safely.
Police forces across the region have been paying tribute to an officer killed during the terror attack in Westminster.