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Distribution of individual wave overtopping volumes at rubble mound seawalls
Abstract For a safe design of a rubble mound seawall, overtopping characteristics such as the mean overtopping discharge (q) and the maximum individual overtopping volume (V max) should be limited. Unlike q, the estimation of V max is more complex and requires a wave-by-wave analysis of overtopping as well as a statistical analysis. The present study contributes to the knowledge of the distribution of individual overtopping volumes and the estimation of V max at rubble mound seawalls. A total of 135, small-scale 2D physical model tests were conducted across a practical range of crest freeboards and considered the slopes of 1:1.5 and 1:2. The well-known 2-parameter Weibull and Exponential distributions were first fitted to the experimental data to estimate the V max. Different approaches to sample the observed distribution of wave-by-wave overtopping volumes were evaluated including a threshold method using the top 10%, 30%, and 50% of individual overtopping volumes, and a method that applies a greater weighting to the larger events. For both Weibull and Exponential distributions, the weighted method was found to be the best one providing a 23% and 17% decrease in scatter index (SI) values compared to the best of existing methods. To facilitate the estimation of V max for design purposes, a simple empirical formula was developed as a function of the dimensionless mean overtopping discharge (q*) and the number of overtopping waves (N ow). This formula with SI = 37% outperformed the distribution-based methods as well as the best of existing formulae for V max. In the case of the normalised bias (NBIAS), the distribution methods underestimated V max by −21% (Weibull) and −31% (Exponential) whereas the new formula yielded NBIAS = −6%.
Highlights 135 wave-by-wave small-scale 2D physical model tests were conducted on rubble mound seawalls. Existing formulations underestimate the maximum individual wave overtopping volume (V max). Weibull and exponential distributions were fitted to the data and improved formulations were proposed to Vmax. Weighted approach provided a more accurate estimation of Vmax compared to approaches using only the higher part of volumes. A more accurate and simple formula (based on of q* and N ow) was proposed for the estimation of V max .
Distribution of individual wave overtopping volumes at rubble mound seawalls
Abstract For a safe design of a rubble mound seawall, overtopping characteristics such as the mean overtopping discharge (q) and the maximum individual overtopping volume (V max) should be limited. Unlike q, the estimation of V max is more complex and requires a wave-by-wave analysis of overtopping as well as a statistical analysis. The present study contributes to the knowledge of the distribution of individual overtopping volumes and the estimation of V max at rubble mound seawalls. A total of 135, small-scale 2D physical model tests were conducted across a practical range of crest freeboards and considered the slopes of 1:1.5 and 1:2. The well-known 2-parameter Weibull and Exponential distributions were first fitted to the experimental data to estimate the V max. Different approaches to sample the observed distribution of wave-by-wave overtopping volumes were evaluated including a threshold method using the top 10%, 30%, and 50% of individual overtopping volumes, and a method that applies a greater weighting to the larger events. For both Weibull and Exponential distributions, the weighted method was found to be the best one providing a 23% and 17% decrease in scatter index (SI) values compared to the best of existing methods. To facilitate the estimation of V max for design purposes, a simple empirical formula was developed as a function of the dimensionless mean overtopping discharge (q*) and the number of overtopping waves (N ow). This formula with SI = 37% outperformed the distribution-based methods as well as the best of existing formulae for V max. In the case of the normalised bias (NBIAS), the distribution methods underestimated V max by −21% (Weibull) and −31% (Exponential) whereas the new formula yielded NBIAS = −6%.
Highlights 135 wave-by-wave small-scale 2D physical model tests were conducted on rubble mound seawalls. Existing formulations underestimate the maximum individual wave overtopping volume (V max). Weibull and exponential distributions were fitted to the data and improved formulations were proposed to Vmax. Weighted approach provided a more accurate estimation of Vmax compared to approaches using only the higher part of volumes. A more accurate and simple formula (based on of q* and N ow) was proposed for the estimation of V max .
Distribution of individual wave overtopping volumes at rubble mound seawalls
Koosheh, Ali (author) / Etemad-Shahidi, Amir (author) / Cartwright, Nick (author) / Tomlinson, Rodger (author) / van Gent, Marcel R.A. (author)
Coastal Engineering ; 177
2022-07-01
Article (Journal)
Electronic Resource
English
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