Storm-Surge Hindcast at Viana do Castelo: An Oceanic and Estuarine Domain Approach

Abstract

Marujo, N.R.C.S.; Araújo, M.A.V.C., Trigo-Teixeira, A.; Falcão, A.P., and Mazzolari, A., 2014. Storm-surge hindcast at Viana do Castelo: An oceanic and estuarine domain approach.In the present work a storm-surge event, which occurred in Viana do Castelo (Portugal) on 14–17 October 1987, is modelled using the advanced circulation model (ADCIRC) . The main purpose of the work is to investigate the ability of ADCIRC to model storm-surge events in the region. Modelling this type of phenomena is of the utmost importance to comply with the European Union directive 2007/60/CE, concerning the assessment and risk management of floods, and to create risk charts used in coastal zone management. During this process, a strong emphasis was given to model calibration before storm-surge modelling. Preceding model calibration a field survey, using global navigation satellite system techniques, was carried out in the Lima Estuary to acquire lacking information required to build the corresponding digital terrain model (DTM). While modelling storm surge, two different domains were considered: a large oceanic and a smaller estuarine. For each of these domains, the model was calibrated with astronomy forcing using, respectively, the 6 and 10 most important tidal constituents, which were determined by harmonic analysis of the Viana do Castelo tidal gauge record. The friction coefficient, wave continuity, and lateral viscosity parameters were changed with this aim. Although the friction coefficient proved to be the most important calibration parameter, the other parameters are also important to achieve stable simulations. For the oceanic domain, the obtained results were improved by considering a variable Coriolis factor. Once the model was calibrated, it was forced using astronomy and meteorology jointly and separately. Atmospheric pressure, wind, and, for the estuarine domain, also river flow were considered as meteorological agents. The storm event was satisfactorily reproduced by the model and it was concluded that meteorology and astronomical effects interact nonlinearly. This nonlinearity is more pronounced when considering the river flow due to the tidal wave–current interaction.