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Runup is one of the most important factors affecting the design of revetments exposed to wave action. Generally, riprap revetments are designed so that little or no runup exceeds the top of the protection. In the past this has been a difficult prediction to make, but now a new method for calculating the approximate upper limit of wave runup on riprap has been formulated. This method is based on laboratory data and is easy to apply through use of a recommended or an alternative formula. The recommended formula uses the Airy wavelength, LP, while the alternative formula uses the more standard deep-water wavelength, Lo. The alternative formula provides an easy way to calculate a good ``rule-of-thumb'' estimate for runup. Both formulas can be used to compute the elevation to which protection needs to be extended to prevent exceedance by runup, or used to estimate potential severity of wave overtopping.

This paper discusses recent laboratory tests of irregular wave overtopping of coastal structures being conducted at the Coastal Engineering Research Center (CERC). Current model tests of seawalls has led to an improved method for predicting wave overtopping rates. Structures tested included seawalls fronted by a variety of riprap revetment configurations as well as a seawall with no fronting revetment. Overtopping rates have been found to be strongly dependent on a dimensionless parameter, F' , which is the ratio of the freeboard of the seawall to a measure of the severity of the incident waves. The parameter, F' , contains several variables including the crest elevation of the seawall, the local water level and depth, the zero-moment wave height, and the period of peak energy density of the wave spectrum. A simple exponential model incorporating F' is useful for evaluating and comparing the performance of various seawall/revetment configurations and can be used to compute realistic wave overtopping rates.

Results from an extensive series of laboratory tests of irregular wave overtopping for a number of seawall and seawall/revetment configurations is presented. Data for 13 configurations has been collected and grouped into 7 data sets representing relatively similar geometrical characteristics. All data sets showed an approximately exponential relationship between the overtopping rate and a dimensionless freeboard parameter which is the ratio of the seawall freeboard to the local wave severity. This finding logically led to the development of three progressively more complex overtopping models. The models provide a relatively simple way to estimate overtopping rates and an objective way to evaluate the hydraulic performance of seawalls/revetments. Advantages and disadvantages of the models are discussed and their ability to predict overtopping rates is compared.