SAND BUDGET OF THE DUTCH COAST

P. van Vessem, A. Stolk

Abstract


About 255 kilometer (70%) of the Dutch coast is protected against flooding and storm surges by dunes. Another 43 kilometer is defended by dikes with a sandy nearshore. The sand is transported by physical processes in alongshore and onshore-offshore direction. As a result the coast shows continuous alternations. A detailed sand budget is very useful to gain insight into the dynamics of the coast and of different morphological zones. Within the framework ofthe Coastal Defence Study in the Netherlands recent advances in modelling oflarge scale coastal development were made (Louisse and Kuik, 1990; Stive, Roelvink and De Vriend, 1990). Verification and calibration of these models is possible by comparing the model results with the sand budget of the coast. According to the Shore Protection Manual (1984) the sediment budget is defined as a sediment transport volume balance for a selected segment of the coast. The elements of the budget are processes that increase (sources) or decrease (sinks) the quantity of sand in a defined control volume. Usually a sand budget analysis is made to calculate an unknown erosion or deposition rate by estimating the different elements of the budget like for instance longshore transport, on- and offshore sand movement and the building or erosion of dunes. The method is clearly described by Bowen and Inman (1966) and Chapman (1981). The balance itself is defined by Bowen and Inman (1966) and Komar (1983) as the component of the budget that gives the net gain or loss of sand in a control volume. This balance is obtained by monitoring the erosion or deposition rate over a number of years. This paper is concerned with the sand balance of the Dutch coast over the years 1965 - 1986. A method for calculating the balance based on yearly measured profiles is described. Besides the more general results for the Dutch coast a more detailed example of the Schouwen peninsula is given.

Keywords


sand budget; sediment budget; Dutch Coast

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