However, in all these studies only short waves are considered, whereas longer waves generated by wave groups are
expected to play an important role in the hydrodynamics and sediment transport processes within mangrove systems as
suggested by Massel, Furukawa, and Brinkman (1999). The mildly sloped mangrove beaches and their even more gently
sloping foreshores create dissipative conditions in which the incident wind and swell waves dissipate most of their energy
before reaching the shoreline. At the edge of the mangrove forests the longer infragravity band will therefore already
substantially contribute to the water surface variance. Within the mangrove forest this effect is enhanced since
longer-period waves such as swells and infragravity waves are subject to less attenuation, whereas short-period waves
with frequencies related to wind waves lose substantial energy due to stronger interactions with the vegetation. To
consider the effect of both incident waves and infragravity waves, the XBeach model was used in this study to provide
insight into the wave attenuation in mangrove forests and to evaluate the critical value of mangrove width as found for the
east coast of Vietnam in more quantitative terms