Overwash experiment on a sandy barrier

Ana Matias, Gerd Masselink, Art Kroon, C Blenkinsopp, I.L. Turner

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24 Citations (SciVal)


This paper uses results obtained from the large-scale BARDEX II experiment undertaken in the Delta flume to
investigate the morphological response of a prototype sandy barrier to wave and tidal forcing during overwash
conditions. Since overwash processes are known to control short-term barrier dynamics and long-term barrier
migration, the development of a robust quantitative method to define the critical conditions leading to barrier overwash
is important both for scientific and practical management purposes. The Overwash Potential (OP), defined as the
difference between the wave runup and the barrier elevation is used to define the overwash threshold condition, and to
predict the morphological outcome of a particular overwash event. When OP is negative, wave runup is lower than the
barrier crest and insignificant morphological changes are noticed at the barrier crest. When OP is positive, overwash
occurs because predicted runup elevation is higher than the barrier crest. When OP is close to zero, overtop is expected
with limited intrusion of water across the top of the barrier crest. To make effective use of OP it is necessary to identify
a reliable runup predictor. Twelve runup equations were tested for this purpose, and the results were compared with the
ones obtained using data from BARDEX experiment on a gravel barrier. A most reliable approach for the determination
of OP for sandy barrier was similar to gravel barrier overwash experiments, with runup predictions provided by the
equation of Stockdon et al. [Stockdon, H.F., Holman, R.A., Howd, P.A.,Sallenger, A.H., 2006. Empirical
parameterization of setup, swash, and runup. Coast. Eng., 53, 573-588]. This is striking, since different runup predictors
would have been expected because beach slope, hydraulic conductivity, grain-size, amongst other factors, differ for
both types of barriers. Nevertheless, the two main morphologic characteristics for the computation of OP are beach
slope and the barrier crest elevation, both accounted for in the proposed equation. The use of OP values provides a
practical means by which to identify potential coastal hazards associated with barrier overwash processes and is
considered to have a range of practical coastal management applications.
Original languageEnglish
Pages (from-to)778-783
Number of pages6
JournalJournal of Coastal Research
VolumeSI 65
Publication statusPublished - 2013


  • runup
  • storm
  • coastal hazard


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