Swash zone sediment fluxes: field observations

C.E. Blenkinsopp, I.L. Turner, G. Masselink, P.E. Russell

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

This paper describes newly obtained, high-frequency observations of beach face morphological change over numerous tidal cycles on a macrotidal sandy beach made using a large array of ultrasonic altimeters. These measurements enable the net cross-shore sediment fluxes associated with many thousands of individual swash events to be quantified. It is revealed that regardless of the direction of net morphological change on a tidal time scale, measured net fluxes per event are essentially normally distributed, with nearly equal numbers of onshore and offshore-directed events. The majority of swash events cause net cross-shore sediment fluxes smaller than ±50kgm and the mean sediment flux per swash event is only O(±1kgm) leading to limited overall morphological change. However, much larger events which deposit or remove hundreds of kilograms of sand per meter width of beach occur at irregular intervals throughout the course of a tide. It was found that swash-swash interactions tend to increase the transport potential of a swash event and the majority of the swash events that cause these larger values of sediment flux include one or more interactions. The majority of the larger sediment fluxes were therefore measured in the lower swash zone, close to the surf/swash boundary where swash-swash interactions are most common. Despite the existence of individual swash events that can cause fluxes of sediment that are comparable to those observed on a tidal time scale, frequent reversals in transport direction act to limit net transport such that the beach face volume remains in a state of dynamic equilibrium and does not rapidly erode or accrete.
Original languageEnglish
Pages (from-to)28-44
Number of pages17
JournalCoastal Engineering
Volume58
Issue number1
Early online date9 Aug 2010
DOIs
Publication statusPublished - 1 Jan 2011

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