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.

Breaching is the most frequent form of embankment failure in the world. Due to overtopping, an embankment starts to breach when part of the embankment actually breaks away, leaving an opening for water to flood the land protected by the embankment. A breach can be a sudden or gradual failure that is caused by surface erosion and/or headcut erosion in the embankment. The magnitude and extent of the losses depend highly on the rate of breaching of the embankment, which determines the discharge through the breach and the speed and rate of inundation of the valley or polder. Therefore, modelling of the breach evolution in embankments is of significant interest for damage assessment and risk analysis. It is also important for the development of early warning systems for dike and dam failures and of evacuation plans for people at risk.
The breach flow plays an important role in the embankment breaching process, coupling the hydraulic process and the sediment transport process. During the breaching process, the flow overtops the entire embankment crest and generates the breach channel in the initial phase of the breach development. As the breach further develops, the breach flow goes only through the breach channel due to the decrease of the upstream water level. The breach flow can thus be classified as compound weir flow and weir flow, each having own special characteristics. In a breach, the helicoidal flow accelerates the sediment undermining at the toe of the breach slopes and widens the breach in the lateral direction of the embankment. A triangular hydraulic jump happens when the breach flow changes from supercritical flow into subcritical flow, with a triangular critical area at the toe of the breach. The triangular hydraulic jump works as a driving force to the headcut erosion in the breaching process and the scour hole development at the toe of embankment. According to the hydraulic energy loss in the breach, the discharge coefficients are deducted for both weir flow condition and compound weir flow condition. The resulting discharge coefficients can be used in the calculation of the breach discharge in a breach model.
In the present study, five runs of breach experiments were conducted in a relative large laboratory flume. The experimental results clearly expose the hydrodynamic process and the erosion process in the breaching of the cohesive embankment. The breaching starts with the initial erosion of the embankment surface washing away the embankment surface. Due to the surface erosion at the toe of the embankment, the headcut erosion is stimulated on the embankment slope. While headcut migration stimulates the breach to develop in longitudinal direction, the lateral erosion triggers the breach to widen in lateral direction. Three types of erosion (surface erosion, headcut erosion and lateral erosion) contribute to the breach erosion process in the embankment, however, the breach flow is the driving force for the erosion. Sediment deposition in the breaching process, generally ignored in the embankment breaching studies, is also of importance.
A mathematical model has been developed that couples weir flow and erosion (surface erosion, headcut erosion and lateral erosion). The breaching process is simplified into initial development, deepening development and widening development, corresponding with surface erosion, headcut erosion and lateral erosion, respectively. As the link between flow and embankment material, erosion plays a key role in the embankment breach model. Mathematical descriptions of the headcut migration and the lateral migration rate have been developed to simulate the breaching process in cohesive embankments. The headcut erosion and the lateral erosion are considered to occur in the form of clay blocks instead of in the form of individual clay particles.