Pevensey Bay Nearshore Monitoring

The mixed, shingle barrier beach at Pevensey Bay, East Sussex, represents a crucial asset in flood defence and coastal risk management along the East Sussex coastline, protecting the low-lying Pevensey Levels, with designated wetlands as well as thousands of vulnerable properties (many built at the crest) and coastal infrastructure. The 9km frontage is highly dynamic and suffers a net loss of sediment due to littoral drift, partly blocked by the Sovereign Harbour breakwater at the southern side (Sutherland and Thomas, 2011). This is managed through continuous bypassing and recycling of beach material, as well as regular beach nourishment and repair of key groynes, following a major capital recharge scheme in 2002. This is operated under a unique, private finance initiative, to provide a 1:400 year standard protection against breaching and maintaining a crest elevation. The spatial and temporal variations in beach volume, erosion and rollback remain poorly understood, and interventions to redistribute beach material are continuous. Furthermore, the beach experiences lowering of the sandy foreshore, though the exact drivers for this remain unknown. A better understanding of the dynamics of this barrier is thus needed to inform future management. The aim of the project is to apply a novel method for measuring shoreface processes (in shallow waters with a tidal range of 6.1 m), with an emphasis on wave propagation/ transformation and sediment transport across the very shallow nearshore (out to approximately 6m CD water depth). To measure nearshore processes, an array of bottom-mounted instruments will be set up across the shallow foreshore, to define wave progression and energy flux across the beach and to measure vertical velocity and suspended sediment profiles, including a measurement near the bed (Figure 1). This will be complemented by a synoptic wave radar and a sustained survey campaign carried out independently of this tender by a contractor and the university staff using their own equipment. It is anticipated that the wave radar array will be in place by October 2020, for a one-year long deployment.