Technical report wave run-up and wave overtopping at dikes

Abstract

This report is from Dutch origin and is a translation into English. In the Netherlands it is used as a guideline for safety assessment and design of dikes. Assessment of the required dike heights for wave run-up and wave overtopping is important in the Netherlands and has a long history. Some parts of this report, therefore, refer tot typical Dutch situations. Nevertheless, the methods given in the report to determine wave run-up and wave overtopping are for general applications. This Technical Report entitled Wave run-up and wave overtopping at dikes has been composed under the auspices of the TAW and has been based on an investigation [WL, 1993-1] Wave run-up and wave overtopping at dikes, which has been supplemented with additional research and recent views on some less developed aspects. Up to the first half of the 1990s, the Guidelines for the Design of River Dikes, part 2 [TAW, 1989] were mainly consulted for determination of wave run-up and wave overtopping. In Appendix 11 of these guidelines, formulae are presented for wave run-up and wave overtopping, most of which were published earlier in the TAW report Wave run-up and wave overtopping [TAW, 1972]. Considering that wave run-up heights and wave overtopping discharges are greatly involved in the determination of the total crest height of a dike, it is more than obvious that a great deal of study has been carried out in recent years into these aspects. As a result, a large amount of knowledge has been acquired over time in the area of the influence of roughness, slope angle, berms, angle of wave attack and vertical walls on wave run-up and wave overtopping. Results on the effects of shallow and very shallow foreshores have also been received recently. Although the formulae for determining wave run-up and wave overtopping were until recently intended for deterministic calculations, they are now regularly being applied in probabilistic calculations, in which the distribution of the input data and uncertainty in the constants are included. This puts strict requirements on the formulae with regard to the continuity and validity of the functions. A great deal of experience has already been gained by various users from the intermediate results of the study and draft versions of this report. Recommendations from the users have led to improvements in the usefulness of the new formulae. The areas of validity of the new formulae have also been determined. This does not mean that the formulae can be applied to every profile and all wave conditions without exception. Indeed, it is for these complex situations outside the areas of validity that craftsmanship will still be required. The new wave run-up and wave overtopping formulae replace the existing formulae as given in the Guideline for design of river dikes, part 2 [TAW, 1989]. The new formulae can be applied in the design and safety assessment procedures for river dikes. The new formulae will also be or even are being included in the safety assessment procedure for the dikes along the IJsselmeer. For dikes along the coast and estuaries, sometimes shallow or very shallow foreshores occur which lead to deviant wave spectra, possibly in combination with long waves. Although research has not yet completely crystallised, it has been decided to include recent results and to adjust the formulae where necessary so that they can also be applied in this type of situation. Specially, for very shallow foreshores the wave run-up turns out to be a little higher than in the past.