Find out about wave and inundation models.

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A Complex task

Coastal inundation in fringing reef environment is not trivial. It is the result of the combined effect of an elevated water level at the reef crest (Tide+surge) and the waves breaking on the reef. The reef flat traps water from the breaking waves on to the reef to create the wave setup. Breaking wave group cause infragravity waves (See more here) which can cause turbulent bores. To be able to predict the extent and intensity of inundation means that you are able to simulate every components that cause the inundation (Figure below. light blue: tide; dark blue: wave setup; orange: infragravity waves (RMS amplitude); red: short wave (RMS amplitude)).


Numerical models

There are only a few models that can capture the interaction of waves, wave groups and water level. In the WACOP project the XBeach model was used. In fact 3 different versions of XBeach were tested and used in the WACOP project.

Maui Bay bathymetry

The bathymetry data collected in maui BAy was interpolated to a 5m resolutuion grid and rotated so the offashore edge faces the West. (More info here)


Interpolated bathymetry at 5m resolution for Maui Bay

Model validations

The model has been validated against the 3 largest wave events measured in Maui Bay (More info here)

Date Crest ZS error (m) Crest HRMS error (m) Crest IGRMS error (m) Shore ZS error (m) Shore HRMS error (m) Shore IGRMS error (m)
30-05-2013 0.28 0.17 0.12 0.01 0.04 0.01
06-06-2013 0.06 0.01 0.05 0.05 0.00 0.06
22-06-2013 0.24 0.17 0.50 0.07 0.02 0.01

Modelling results

The model can then be used to predict areas where the infragravity waves are the largest, where the wave setup is higher and better understand the vulnerability of different part of the coast.

Mean water level (Wave setup)


Short wave height (RMS)


Infragravity wave height (RMS)


Inundation forecasting

The model can also be used to predict the extent of the inundation under different scenarios. Below is the inundation extent for two scenarios:

Minor flood event

Offshore wave height of 4m and hight tide of 0.4m


Major flood event

Offshore wave height of 5m and hight tide of 0.4m


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