PREDICTION OF BEACH PLANFORMS WITH LITTORAL CONTROLS

Marc Perlin, R.G. Dean

Abstract


Three numerical models representing shoreline response are desscribed and applied to a number of problems of coastal engineering interest. Included are: (1) a one-line explict model, (2) a one-line implicit model, and (3) a two-line explicit model. Simplified refraction and diffraction schemes are incorporated into the models. The models allow grid elements to be activated and deactivated as sand is initially deposited in or the last sand removed from a grid at a jetty inclined to the shoreline. The one-line explicit model and twoline explicit model are similar to those described by Bakker, Breteler and Roos'3'. The one-line implicit model offers the advantage of stable computations for much longer time steps. Example applications of shoreline response are presented to illustrate the utility of the model including: permeable versus impermeable jetties, shoreline perturbations caused by jetties which are aligned with the incoming waves versus jetties perpendicular to shore, shoreline response inside a groin compartment and the effect of a littoral barrier. In addition, the one-line implicit model is applied to predict the shoreline response in the vicinity of an offshore breakwater at Channel Islands Harbor, California where sediment is accumulated and dredged periodically. In this case, excellent shoreline response data are available from the prototype; however, only visual wave observations were available for this comparison and it was found necessary to increase the sediment transport relationship fourfold to achieve even approximate correspondence. Numerical models offer a powerful means which, when combined with good judgement, should strengthen the coastal engineer's ability to predict the effects of a coastal engineering design. The research needs to improve numerical modeling capabilities are presented.

Keywords


beach planforms; littoral control; planform prediction; numerical modeling

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