Duration effects of wave overtopping: application of EurOtop on three reservoirs in the North West Available to Purchase

The action of waves on embankment dams combined with high still water levels can have a detrimental impact on reservoir structures. The problem of overtopping has been described in detail in the European overtopping manual (EurOtop) for sea defences. Although this methodology was not developed for inland reservoirs, its application to reservoirs is considered acceptable in certain cases. This paper describes the process of applying the EurOtop methodology to three inland reservoirs, the development of the significant wave height, breaker parameter, wave period and ultimately the overtopping discharge. The EurOtop methodology allows a simple look-up of peak discharges against tolerable discharges to determine whether erosion resistance is required. This paper describes a method to derive a discharge–time relationship based on the probable maximum flood flow through the reservoir and in turn derive the velocity–duration relationship. Using this relationship an additional check of tolerable velocities was performed and checked against recommended limiting values for erosion resistance. Finally, an optioneering exercise was carried out to determine the generic options available to address overtopping discharge.