Beach response to shore-parallel breakwaters at Sea Palling, Norfolk, UK

Abstract

The effects of four offshore breakwaters built between 1993 and 1995 at Sea Palling, Norfolk, UK, on beach morphology are discussed. The structures were built during the first phase of a multi-phase construction programme and are expected to provide long-term protection for Sea Palling and 6000 ha of low-lying land against tidal inundation through the provision of a wide beach in front of the existing seawall and dunes. The results presented here span all stages of breakwater construction during Phase 1. Beach level changes were monitored during the period from 1995 to 1999. A Geographical Information System (GIS) was used to calculate differential surfaces between surveys in order to investigate local patterns of accretion and erosion and to determine volume changes between consecutive surveys. Additional data collected by the Environment Agency since 1991 were analysed to investigate beach and bathymetry changes prior to the construction of the breakwaters. In association with periodic nourishment programmes the scheme has been locally successful in retaining recharged sediment on the beach but the extent of the salients prevents to a great extent the south-eastward littoral drift. As a result, effects on the beaches, both down- and up-drift of the breakwaters, have been considerable. The continuing increase in beach volume indicated that by January 1999 equilibrium had not been reached.