Wave momentum flux parameter: a descriptor for nearshore waves

A new parameter representing the maximum depth-integrated wave momentum flux occurring over a wave length is proposed for characterizing the wave contribution to nearshore coastal processes on beaches and at coastal structures. This parameter has units of force per unit crest width, and it characterizes flow kinematics in nonbreaking waves at a given depth better than other wave parameters that do not distinguish increased wave nonlinearity. The wave momentum flux parameter can be defined and estimated for periodic and nonperiodic (transient) waves. Thus, it has potential application for correlating to processes responding to different types of waves. This paper derives the wave momentum flux parameter for linear, extended linear, and solitary waves; and it presents an empirical formula estimating the parameter for nonlinear steady waves of permanent form. Guidance is suggested for application to irregular waves. It is anticipated that the wave momentum flux parameter may prove useful for developing improved semiempirical formulas to describe nearshore processes and wave/ structure interactions such as wave runup, overtopping, reflection, transmission, and armor stability. Surf zone processes where waves break as plunging or spilling breakers may not benefit from use of the wave momentum flux parameter because the breaking processes effectively negates the advantage of characterizing the wave nonlinearity. D 2004 Elsevier B.V. All rights reserved.