Wave set-up in the modeling of storm surge at Viana do Castelo (Portugal)

This work presents the hydrodynamic modeling of a storm surge event that hit the Portuguese coast during the period of 14th-16th October 1987. The effect of wave set-up on the storm surge water levels at the region of Viana do Castelo was investigated. To study the coupled effects of the surge and waves, the circulation model ADCIRC and the spectral wave model STWAVE were applied. Attending the various forcing mechanisms related with coastal extreme sea water levels, a series of simulations were carried out, first with meteorological input only and then incorporating the radiation stress gradients of the incoming waves. Results show that, when the effect of wave-induced radiation stresses is present, there is an increase in the peak sea level of around 38% compared when wave set-up effect is absent. It was concluded that the inclusion of radiation stress is important in simulating the storm surge water levels at the region of study, however because surge heights are still underestimated when compared the measured surge, further simulation tests including other physical mechanisms are required. Also, simulations involving both tidal and meteorological forcing were performed and the existence of non-linear energy transfer between both forcing mechanisms was found.