Estimating Wave-Induced Kinematics at Sloping Structures

This paper provides a technique for the estimation of root-mean-squared velocity parameters associated with irregular waves that have been reflected by coastal structures. A previously published first-order expression for estimating root-mean-squared water velocities beneath normally incident and reflected nonbreaking irregular waves by Hughes has been empirically augmented so that estimates can be made for the case of smooth impermeable plane sloping revetments and permeable rubble-mound cross sections. Empirical relationships for reflection coefficient and reflection phase were developed based on measurements obtained during laboratory experiments. These relationships, when used in the theoretical formulations, gave reasonable estimates of RMS velocity compared to measured laboratory data. The procedure given in this paper can be applied with a minimum of computational effort, and it provides realistic estimates of irregular wave kinematics near coastal structures. The capability to make these velocity estimates, particularly near the seabed, provides practicing engineers with an improved tool for addressing such problems as scour potential at structure toes and design of suitable scour blankets.