Formulating Wave Overtopping at Vertical and Sloping Structures with Shallow Foreshores Using Deep-Water Wave Characteristics

Christopher H Lashley,Jeremy D Bricker,Jentsje Van Der Meer,Corrado Altomare,Tomohiro Suzuki,Katsuya Hirayama

doi:10.1061/(asce)ww.1943-5460.0000675

Abstract

The state-of-The-Art formulas for mean wave overtopping (q) assessment typically require wave conditions at the toe of the structure as input. However, for structures built either on land or in very shallow water, obtaining accurate estimates of wave height and period at the structure toe often proves difficult and requires the use of either physical modeling or high-resolution numerical wave models. Here, we follow Goda's method to establish an accurate prediction methodology for both vertical and sloping structures based entirely on deep-water characteristics-where the influence of the foreshore is captured by directly incorporating the foreshore slope and the relative water depth at the structure toe (htoe/Hm0,deep). Findings show that q decreases exponentially with htoe/Hm0,deep due to the decrease of the incident wave energy; however, the rate of reduction in q decreases for structures built on land or in extremely shallow water (htoe/Hm0,deep ≤ 0.1) due to the increased influence of wave-induced setup and infragravity waves-which act as long-period fluctuations in mean water level-generated by nonlinear wave transformation over the foreshore.

Highlights

BackgroundCoastal engineers rely on empirical formulas to predict the volume of water that passes over the crest of coastal structures due to wave action during storms
We focus on smooth structures under very shallow conditions; we focus on the diagrams developed for vertical walls with htoe/Hm0,deep < 1
Foreshore Effect on Nearshore Conditions In order to establish accurate wave overtopping formulas based on deep-water wave characteristics, the effects of shallow foreshores on wave conditions at the toe of the structure need to be accurately parameterized

Summary

Introduction

Coastal engineers rely on empirical formulas to predict the volume of water that passes over the crest of coastal structures due to wave action during storms. This process, known as wave overtopping, can result in damage to critical infrastructure and even loss of life. The state-of-the-art empirical models for wave overtopping of sloping structures (EurOtop 2018), including that of Altomare et al (2016) and Van Gent (1999) developed for shallow foreshores, typically require wave parameters at the toe of the structure as input—namely significant wave height (Hm0,toe) and spectral wave period (Tm−1,0,toe). One major drawback is that for very shallow conditions, with heavy wave breaking, obtaining accurate estimates at the toe typically requires either physical model tests or high-resolution numerical models capable of capturing the nonlinear effects of wave transformation over the foreshore (Mase et al 2013)

Objectives

Methods

Results

Conclusion