An accurate prediction of shoreline changes behind detached breakwaters is, in regard to the adjustment to the environmental impact, still a challenge for designers and coastal managers. This research is expected to fill the gaps in the estimation of shoreline changes by developing new and generalized relationships of the shoreline changes to the detached breakwaters at several sensitive points, based on varying structure parameters, physical conditions and sediment properties of the prototypes. The generalization of relationships is intended to create new predictive possibilities. Chapter 2 presents the changes of waves and currents, leading to morphological changes in the sheltered areas of the breakwaters. As a consequence, the various positions of breakwaters’ field change the morphology on the shoreline, such as the center of a structure, the shoreline opposite a gap, the up-drift and the down-drift position. To solve these problems, several methods are used to investigate the shoreline response, such as numerical, physical, and empirical models. In chapter 3, the prototype approach is used as justifiable data for the development of the relationship models. In total 93 projects with 1144 structures were collected, including structure parameters, physical conditions, sediment properties and shoreline result measurements. The structural parameters are collected from a variety of sources, such as inquiry questionnaires, project reports, a selection of specific articles, journals and papers. The structural aspects, such as length of breakwater, offshore distance, gap width, freeboard, crest width, water depth at structure and structure orientation, are collected. The physical condition data, including wave, current and tidal range, were retrieved from online scientific resources and organizations. In chapter 4 the predictive relationships of the shoreline changes are developed with the different accretion formations and the shore positions. The models start with the findings of the basic relationships of the shoreline changes and continue with the development of the relationships of the shoreline changes including the other parameters. The collective relationships of the shoreline changes are a combination of the total effects. The new relationships are developed to estimate the siltation of tombolo, salient and limited response; for the shoreline opposite the gap, for the up-drift and the down-drift. All these relationships are analysed for the goodness of fit (R-squared), the error of estimate and the correlation coefficients of the regression. Further on in this chapter, several existing models of the relationships are compared with the new basic relationships. However, there are no previous relationships to be compared with the complete relationships. In chapter 5 the quantitative individual parameter effects on the shoreline changes are interpreted. The shoreline change functions relate to multiple parameters, therefore, the effect of each parameter needs to be analysed, while keeping the other parameters unchanged on the shoreline results. Comparison between the degree of the shoreline changes caused by the different parameters, thus, will show which parameters have more influence on the shoreline changes.@en