WWII sea wall in St Aubin’s Bay, Jersey: infrastructure improvements to alleviate flooding

Abstract

The sea defences constructed by the occupying Germans in 1943 are widespread in Jersey, and most still function today. The particular length of sea wall east of the slipway at Gunsite Café in St Aubin’s Bay had experienced overtopping during high tides and storm events for many years, resulting in flooding inland at the main roundabout leading to the airport. The wall is subjected to 12 m tidal range. Engineering investigations into the causes of the flooding were started in 2014 to determine the nature of the flooding and how the mass concrete, original World War II (WWII) sea wall played a major part in it. The scope of the overall project included investigations into the flooding, the research into the original WWII mass concrete wall and design of a concrete capping beam with a recurve that allowed the top of the wall to be raised. Phase 1 of the construction work was completed in October 2017. Digital modelling together with innovative construction engineering methods enabled the project to be completed reducing the large wave forces which impact on this wall to be resisted even under storm conditions. This paper describes the investigations, research and design work involved in arriving at a design solution.