![]() Whilst these observed slope effects are too large to be ignored, they still need to be verified by tests using physical models. Since present design guidelines for non-breaking waves do not include the effect of the slope angle, modified guidelines have also been proposed. In the case of overtopping at rubble-mound breakwaters, recent research using numerical models indicates that overtopping is strongly dependent on the slope angle. The official website of the EurOtop Manual, which is widely used in the design of coastal engineering structures, features a number of visualisations of wave overtopping. Overtopping follows the cyclical nature of waves, resulting in a large amount of water flowing over a structure, followed by a period with no water. ![]() Overtopping is typically expressed in litres per second per metre of dike length (L/s/m), as an average value. The freeboard is the height of the dike's crest above the still water level, which usually corresponds to the determining storm surge level or river water level. In such instances, a probabilistic calculation is necessary. This phenomenon is inconsequential when water levels and wave heights exhibit correlation however, it poses difficulties in river systems where these factors are uncorrelated. Overtopping can transpire through various combinations of water levels and wave heights, wherein a low water level accompanied by high waves may yield an equivalent overtopping outcome to that of a higher water level with lower waves. The amount of overtopping depends on factors including the freeboard, wave height, wave period, and slope of the dike. These effects may be further intensified when the storm coincides with a high spring tide.Įxcessive overtopping may cause damage to the inner slope of the dike, potentially leading to failure and inundation of the land behind the dike, or create water-related issues on the inside of the dike due to excess water pressure and inadequate drainage. Wave overtopping typically transpires during extreme weather events, such as intense storms, which often elevate water levels beyond average due to wind setup. Excessive overtopping is undesirable because it can compromise the integrity of the structure or result in a safety hazard, particularly when the structure is in an area where people, infrastructure or vehicles are present, such as in the case of a dike fronting an esplanade or densely populated area. When waves break over a dike, it causes water to flow onto the land behind it. Wave overtopping is the time-averaged amount of water that is discharged per linear metre by waves over a structure such as a breakwater, revetment or dike which has a crest height above still water level. Wave overtopping in Vlissingen during a storm, 1953 or 1954 Overtopping on the inner slope of a dike in Northern Germany during a storm, 1954 Wave overtopping and wave run-up at a coastal structure Transmission of water waves over a coastal structure
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