Individual violent wave-overtopping events: behaviour and estimation

Alison Raby*, Ravindra Jayaratne, Henrik Bredmose, Geoff Bullock

*Corresponding author for this work

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To better understand individual violent wave overtopping, of significance for coastal defence design, three breaking wave types (steep-fronted, plunging and broken) based on focused wave groups, were generated in laboratory and numerical models. High-speed video captured overtopping events and produced velocity vector maps by means of bubble image velocimetry (BIV). Results were compared with a numerical model based on a linear wave detection procedure and a two-phase incompressible Navier–Stokes-based solver. This novel approach revealed that the overtopping waves comprised an initial jet of 0.2 s duration, but dominated by quasi-steady flow. Whilst laboratory surface-elevation time-histories were highly repeatable, overtopping volume repeats were sensitive to the breaker type. Measured volumes were compared with: the numerical model (which over-predicted, but was reasonably accurate for steep-fronted waves); estimations based on BIV results (which provided very close agreement for the steep-fronted waves); and a weir-based analogy (which provided reasonable agreement, but always under-predicted).
Original languageEnglish
JournalJournal of Hydraulic Research
Issue number1
Pages (from-to)34-46
Number of pages13
Publication statusPublished - 2020

Bibliographical note

© 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


  • Breaking waves
  • Bubble image velocimetry
  • Coastal engineering
  • Flow visualization and imaging
  • Incompresible Navier-Stokes solver
  • Laboratory studies
  • Violent wave overtopping


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