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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. [Copyright &y& Elsevier]

Estuarine beaches are ubiquitous, yet understudied, coastal systems. The mixed hydrodynamic processes – such as combined tidal and wave forcing – and the influence of adjacent sedimentary features – such as flood-tide deltas (FTDs) – leads to complex morphodynamic processes. As such, the dynamics and evolution of these important coastal systems are poorly understood. This study synthesises a set of analyses conducted on an estuarine beach, in southeast Australia, over multiple temporal scales. Nearshore waves and currents were measured and used to determine the processes driving seasonal to yearly beach change between 2007 and 2010. These results were compared to decadal scale beach change determined from aerial photos between 1963 and 2006. We found the westward transport of sediment towards the inner estuary was the dominant nearshore process leading to erosion in the eastern regions of the beach (near the estuary entrance) and accretion in the west over yearly time scales. Cross-shore sediment transport occurred during winter storm swell conditions leading to erosion in more exposed sites and some limited accretion in sheltered zones, most likely due to sediment input from the flood-tide delta. However, severe storm swell events that propagated into the estuary led to a loss of sediment and erosion across the entire beach which was not recovered during the study period. It is likely that the erosion processes observed in the short- to medium-term (days to years) analyses are the conditions that led to the long-term shoreline retreat observed in the aerial photograph record. The long-term shoreline retreat since 1963 is likely a result of a negative sediment balance due to movement of the FTD and a lack of sediment input in the eastern regions of Shoal Bay. Shoreline retreat will likely continue unless increased sediment input occurs from marine sources or shoreline interventions are maintained. • Multi-scaled morphodynamics of an estuarine beach was investigated. • Beach rotation was observed driven by seasonal cross and long-shore processes. • Over 40 years of chronic storm driven erosion underlies seasonal beach dynamics. • Shoreline retreat is likely driven by a lack of sediment input from marine sources. [ABSTRACT FROM AUTHOR]

The morphological response of a wave-dominated embayed beach to large storms was investigated via field data collection and numerical simulation. Hydrodynamic and morphological field data collected in Haeundae Beach facing SSE in the south-eastern corner of Korea were analysed. During the southerly storm waves (i.e. almost shore-normal direction), the upper part sediments of the beach were eroded, and redistributed to the surf zone. Meanwhile, easterly storm waves transported sediment from east to west, resulting in coastline advancement in the west, and retreat in the east. In order to investigate the morphological response of the beach with limited sediment availability under storm conditions, the numerical model XBeach was used. With the assumption of unlimited sediment availability, the southerly storms led to overestimation of sediment transports, and unrealistic erosion and deposition patterns in the middle part of the beach. In contrast, the model results with the option of sediment layer thickness showed good agreement with the erosion and deposition patterns analysed from field data. This suggests that sediment availability can be one of the key factors in determining the morphological response in a wave-dominated embayed beach, where sediment supply from neighbouring beaches or rivers is limited. • Shore-normal storm waves erode and redistribute the upper part sediments of the beach to the surf zone. • Easterly storm waves result in coastline advancement in the west, and retreat in the east. • Unlimited sediment thickness in simulation leads to overestimation of sediment transports, and unrealistic beach erosions. • Consideration of sediment layer thickness in numerical simulation shows good agreements with the observations. • Sediment availability can be a key factor in determining the morphological response in a wave-dominated embayed beach. [ABSTRACT FROM AUTHOR]

Mixed sand and gravel beaches pose special management issues as they are morphologically distinct from either pure sand or shingle beaches. On the mixed sand and gravel beaches of the Canterbury Bight, New Zealand, displacement of sediments operates within a two-part sediment transport system. The large sediments are retained in the beaches, while the fine sand, silt, and mud are transported offshore to the continental shelf. While the susceptibility of sediments to size-reduction is dependent on the textural mixture of sediments, the actual size-reduction takes place during sediment transport, or displacement, in the active surf zone of the beach. The authors outline a method that incorporates the sediment reduction susceptibility of beach sediments from the textural mixture, twenty years of wave-hindcast data, and sediment tracer experiments to model sediment displacement in mixed sand and gravel beach environments of the Canterbury Bight. Results show that the textural mix of the sediments influences not only the rate of loss to size-reduction but also the time taken for sediment to be transported along a beach continuum within the surf zone. The authors modelled time-frames to achieve three target percentages of sediment displacement: (1) ten percent, (2) fifty percent, and (3) a range of zero to one hundred percent. Ten percent displacement of sediments was predicted to take between four and eighty-eight weeks, fifty percent displacement between one and sixteen years, and a hundred percent displacement up to two-hundred and thirty years, depending on the textural composition of sediments along the coast based on the actual wave action occurring along this coastline. [ABSTRACT FROM AUTHOR]