Linear evolution of a shoreface nourishment

Abstract

The morphological evolution of a shoreface nourishment is investigated by interpreting the nourishment as a linear perturbation of the natural system. The nourishment is projected onto the subset of linear eigenmodes with negative growth rates of the morphodynamical system. The evolution of these linear modes then determines the temporal behaviour of the shoreface nourishment. The method is presented, and results are shown for shoreface nourishments of different length scales on a straight coast and subject to normal incidence. Shoreface nourishments are represented by their expansions according to the projection method on a 1:50 plane beach profile. All nourishments are shown primarily to be diffusive features, with long scale nourishments diffusing more slowly than shorter length scale nourishments. Long scale nourishments also exhibit a shoreward movement during their decay. This all indicates that long length scale nourishments may be more beneficial in coastal engineering projects. This study is a first step towards nonlinear projection to study shoreface nourishment behaviour.