Abstract
Beach nourishment is a viable engineering solution for shore protection by stabilizing beaches. However, beach nourishment may not be technically or economically feasible or justified for some sites, particularly those with high erosion rates. The frequency of re-nourishment is one of the important parameters that could be used to justify beach nourishment process for a given shoreline. Mathematical models could be effectively used for the above purpose. A mathematical model was developed for the simulation of shoreline changes due to both the longshore and crossshore sediment transport and there by, frequency of re-nourishment could be estimated. This model is an improved version to the typical'one-line model'. The model has been calibrated and verified against the field data collected from a beach nourishment project implemented in 2003 in a coastal stretch leading from Maha Oya to Lansigama in the west coast of Sri Lanka. The model results proved that the model is capable of simulating shoreline changes with a reasonable accuracy. Median grain size of beach sand and depth of closure are more sensitive to the model predictions compared to other input parameters. The applicability of the model is limited to straight coastlines without the presence of structures.
Highlights
Beach nourishment is a viable engineering solution for shore protection by stabilizing beaches
In order to calibrate and verify the proposed model, necessary data were collected from a beach nourishment project carried out in the west coast of Sri Lanka in 2003 which was initiated by the Coast Conservation
A mathematicai model was developed for the simulation of shoreline changes due to both the longshore and cross-shore sediment transport
Summary
A basic assumption in one-line model is that the aciive beach profile moves in parallel to itself within a certain closure depth, beyond which the longshore sediment transport can be ignored and the profile does not change. Applying the sediment continuity equation where the volumes of sand entering and leaving a particular cell are considered 1), the change of shoreline position can be computed using the following equation; Figure 1 - Sketch of sediment balance. -,tQz---ddtQ, z z.ax whete, Qr is the volume rate of longshore transport, q is the volume rate of sediments from an external source, f is the time, Dc is the closure water depth. One of the major shortcomings of this model is the omission of cross-shore sediment movement which is an important physical process in certain coastal stretches
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