Wind-wave transformations in an elongated bay

In order to determine wave transformations in an elongated bay, a numerical solution was used to interpret yearlong records of bottom pressure and wind velocity obtained at the mouth and head of Concepción Bay, on the Gulf of California side of the Baja California peninsula. Observed wind waves were predominantly produced by southeastward winds in the winter and north–northwestward winds in the summer. Typical mean wave periods at the bay entrance were between 3 and 5 s. In contrast, the waves at the head of the bay had predominant periods <3 s. The energetic long-period swell waves were dissipated somewhere in the bay as they were not observed at the head of the bay. This study centered in identifying the effects that caused swell waves to attenuate in the bay. The ‘Simulating WAves Nearshore (SWAN)’ model was used to determine the cause for such wave attenuation. Model results showed that swell waves were attenuated because of the combined effects of bottom friction, wave breaking, whitecapping, refraction and wave blocking by the coastline. Most of the attenuation (close to 90%), however, was caused by wave blocking owing to the change of coastline orientation of the bay. This wave blocking mechanism should therefore be explored further in embayments of complex coastline morphology.