Time-Averaged Probabilistic Model for Irregular Wave Runup on Coastal Structures

An experiment was conducted to examine the probability distributions of the waterline elevation on a stone revetment with a 1:2 slope located in the surf zone on a gently sloping beach. The experiment consisted of 27 tests for three spectral peak periods and nine water depths at the toe of the revetment. For each test, 10 wave gauges were utilized to measure the irregular wave transformation from outside the surf zone to the revetment. A runup wire was placed parallel to the revetment to measure the waterline oscillations. An acoustic Doppler velocimeter was also utilized to measure the fluid velocities at the toe of the revetment. The wave reflection coefficients, estimated using a three-gauge array placed just seaward of the surf zone, were less than 0.4. The measured time series and spectra indicate the dissipation of incident waves and the generation of low-frequency waves as the water depth was decreased at the toe of the revetment. The exponential gamma distribution, with measured mean, standard deviation, and skewness, can describe all of the measured probability distributions adequately for all of the tests. The time-averaged model CSHORE predicts the measured cross-shore variations of the mean, standard deviation, and skewness fairly well, although CSHORE underpredicts the standard deviation of the waterline elevation noticeably as the toe depth is increased.