VSBW, a joint venture between VolkerStevin and Boskalis Westminster, will start with the stretch of coast between Long Curtain Moat and Clarence Pier, which is the first of six phases in the project and will take 18 months to complete.
The start of the biggest local authority coastal defence project in the UK comes after more than seven years of planning and public consultation.
Works will include the demolition of the existing seawall and the construction of a compound area with a public information office.
Detailed designs for other phases of the scheme are being developed.
VSBW project manager Neil Dorling said: “We are very pleased to be starting work on the coastal defence scheme in Southsea. VSBW will begin the first phase of work between Long Curtain Moat and Clarence Pier in the coming weeks, whilst we finalise plans. We are keen to make a start on this project that will both enhance and protect the area and the community.”
Councillor Hugh Mason, cabinet member for planning policy and city development, said: "History shows that Southsea has suffered from extreme weather, causing seafront damage and flooding in the past. As our flood defences are ageing, this project is essential if people are to be kept safe. I'm pleased to see works finally getting underway and, while there may be temporary inconvenience, our community will ultimately benefit from the enhanced protection the new coastal defences will offer."