Shore-face nourishments are a common way to protect the coast from eroding. These nourishments interact with near-shore bars, so bar dynamics is an important process that must be understood to perform the nourishments as efficient as possible. The general bar behaviour is clear. Bars move onshore with calm conditions and offshore with storm conditions. The latter is dominant. The bars decay at the end of the bar zone and a new bar forms onshore. However, the factors that influence the bar cycle duration are not completely understood yet. For example, the bar cycle duration for Noordwijk and Egmond is 4 and 15 years respectively. The goal of this report is to find which processes are responsible for the variation in bar migration speed at Noordwijk and Egmond. A Unibest-TC model is used to simulate 10 years of morphological development for both sites. Several simulations are performed with variable wave climate, profile and D50. The results are that it is mainly the steeper profile of Egmond that causes a longer bar cycle duration. Especially the steeper slope of the bar zone gives a lower bar migration speed. This is regulated by the water depth. Initially, at the same water depth, the steeper profile of Egmond gives more sediment transport. This is due to a smaller range of wave breaking above the bar top. However, the bars of Egmond arrive earlier in deeper water, so that wave breaking, sediment transport and offshore bar migration becomes smaller at Egmond. It must be taken in mind that these models are used to find the factors that influence the bar cycle and not to model to morphological development as good as possible. This means that there must be focussed on trends and not on absolute values.
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