Dissimilar Sediments - Model tests of replenished beaches using widely graded sediments (SR350)

Powell, K.A. (1993) Dissimilar Sediments - Model tests of replenished beaches using widely graded sediments (SR350). Technical Report. HR Wallingford, Wallingford.

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Abstract

Commercial pressures on existing offshore aggregate reserves make it likely that within the near future beach replenishment schemes will have to be undertaken using material which is dissimilar from that of natural beaches by virtue of either its size or grading. The behaviour of this material in a beach environment and the consequence repercussions for the design of replenishment schemes is, at present, poorly understood. This report describes research carried out to identify the engineering constraints on the use of this material and to provide preliminary guidance on the design of beach replenishment schemes using dissimilar sediments. The report contains a brief review of previous work and provides details of the experimental investigation undertaken to improve present levels of understanding. A new approach to the design of beach replenishments is outlined. This approach is based on an equilibrium slope concept through which the effects of wave climate and sediment size and grading can be taken into account. The new method has been validated against field data from UK beaches yielding reasonable agreement between predicted and measured equilibrium slopes. Subsequent comparisons against alternative design methodologies based on 'overfill ratios' suggest that the new method, which incorporates wave height and period dependency, produces a substantial improvement in the prediction of beach replenishment requirements, thereby allowing more cost-effective designs to be adopted.

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