Mass, momentum and wave action conservation laws, including the radiation stress, are used to obtain a rip current spacing as an eigenvalue. A coastal region is divided into two parts: offshore region and surf zone separated by a breaker line. Only the case of normal incidence of the waves is considered. From the matching conditions of the two horizontal velocity components at the breaker line, we can obtain rip current spacing as a function of a nondimensional parameter characterizing the surf

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... zone, for an arbitrary value of a parameter indicating the strength of horizontal mixing.