Work has begun on an £8.2m project to repair a flood barrier on the Thames Estuary in Kent.
The Environment Agency said the Dartford Creek Barrier needed a "thorough overhaul" to protect up to 160 homes in the area from flooding.
The barrier consists of two steel gates, weighing 300 tonnes, which are lowered when flooding is likely.
Chains used to lift the gates and other pieces of equipment need replacing, the agency said.
Andrew Pearce, the agency's area manager, said: "After 28 years of good working order, the barrier is due a thorough overhaul."
Work will continue throughout the summer when the risk of flooding is at its lowest.