Abstract
Coastal flooding from wave overtopping causes considerable damage.Presently, to model wave overtopping one can either make use of physicalmodel tests or empirical tools such as those described in the EurOtop manual.Both these methods have limitations; therefore, a quick and reliable numericalmodel for wave overtopping would be a very useful tool for a coastal engineer.This research aims to test and develop a numerical model (in one horizontaldimension) for nearshore waves, runup and overtopping. The Shallow WaterAnd Boussinesq (SWAB) model solves the Boussinesq-type equations of Madsenand Sorensen (1992) for non breaking waves and the nonlinear shallowwater equations for breaking waves. Through testing against a range of physicalmodel data using regular and random waves, the SWAB model’s transferfrom non-breaking to breaking waves was optimised. It was found that a waveheight to water depth ratio worked consistently well as a breaking criterion.A set of physical model tests were carried out, based on previous field testingof wave overtopping that had previously taken place at Anchorsholme,Blackpool. The SWAB model was used to simulate some of these physicalmodel tests, giving good results for mean overtopping rates. SWAB modelsthe force imposed by steep walls and recurve walls on the incident flow; thisforce was found to have a significant effect on overtopping rates. A comparisonwas made between mean overtopping rates from the SWAB model, thephysical model tests, empirically-based software (PC-Overtopping) and thefield data. The physical model and SWAB results compared well with the fielddata, though the empirical software gave large overestimates.The SWAB model was applied to the analysis of overtopping at Walcott,Norfolk. It was found that beach levels affected overtopping rates, but notas much as different randomly phased wave trains. A simulation of a recentstorm event was performed, with overtopping rates being slightly lower thanthose reported by local residents. A joint probability analysis showed that thepredicted frequency of such an event was in line with these reports.An alternative modelling technique was also tested, where a spectral energymodel was coupled with a nonlinear shallow water solver. Results forwave runup parameters were very accurate, when the coupling location isat the seaward edge of the surf zone. Extension of this modelling techniqueinto two horizontal dimensions would be more straightforward than with theSWAB model.
Original language | English |
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Publication status | Published - 2011 |