Sediment concentrations and Sediment transport in case of Irregular breaking waves

Coastal changes occur mostly as a result of changes in sediment transport along the coast. If at cross-section A, the sediment transport is for any reason larger (or smaller) than at cross-section B, accretion (or erosion) will take place in between the two cross-sections. For prediction of coast-lines in the future, the prediction of the net sediment transport is therefore essential. Various models, such as that of Bijker, Van Rijn, Nielsen, Engelund & Hansen and Ackers & White are available to predict the sediment transport by knowledge of wave height and current strength. The reliability of these models is unknown because data under field conditions are scarce. Only few relations between sediment transport, current velocity and wave height are known. For these reasons a laboratory study was carried out to extend the knowledge of the basic phenomena in morphological processes. The study contains experiments in which sediment concentrations and fluid velocities have been measured in case of irregular breaking waves alone and in combination with a current. Chapter 2 deals with the sediment transport basics. Two types of sediment transport, the longshore and the cross-shore sediment transport are discussed and the objectives of the present experiments are presented. In Chapter 3 the experimental set up is described. The measured parameters, methods and instruments are discussed. The experimental programme of the series A and the series B I and B2 are presented. Chapter 4 covers the experimental results from test series A. The wave characteristics, fluid velocities and the influence of these parameters on the sediment concentration, sediment load and sediment transport are studied. Chapter 5 deals with the experimental results from test series B I and B2. The distribution of the sediment concentrations, fluid velocities, sediment loads and sediment transport rates over a sand bar are studied. In Chapter 6 a comparison is made between the measurements and the sediment transport models by Van Rijn and Bijker. Transport rates, concentration profiles and velocity profiles are compared. In Chapter 7 a list of conclusions and recommendations is presented.Hydraulic EngineeringCivil Engineering and Geoscience