Wave reflections in harbours: Reflection performance of rock armoured slopes in random waves

Allsop, W. and Channell, A. (1989) Wave reflections in harbours: Reflection performance of rock armoured slopes in random waves. Technical Report. HR Wallingford.

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Abstract

Wave reflections from sea walls or breakwaters often cause difficulties in the navigation and/or mooring of ships, and may also cause or exacerbate toe scour or local sea bed erosion. Such erosion is a common cause of the failure of many coastal structures. Rock armoured rubble structures often provide efficient energy dissipation reducing both wave run-up levels and wave reflections. This report presents the results of a short series of hydraulic model tests on rock-armoured rubble sea wall sections under random waves. Wave reflections were measured for 9 wave conditions on structures of simple slopes of 1:1.5, 1:2.0, and 1:2-5; and 3 berm widths with upper and lower slopes of 1:1.5. The results of these measurements are presented as values of the reflection coefficient, Cr. The results may be used to predict, and/to to compare, the performance of rock armoured sea walls and breakwaters. The coefficient derived can be used to give boundary conditions for mathematical models of wave action in harbours. The work reported here has been conducted by Hydraulics Research for the British Overseas Development Administration. For further information on this-work, please contact Mr N W H Allsop, manager of the Coastal Structures Section within the Maritime Engineering Department, Hydraulics Research.

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