(1) For breaking waves, Hunt (1959) empirically determined runup as a function of beach slope, incident

wave height, and wave steepness based on laboratory data. Hunt's formula, given in nondimensional form

(Battjes 1974), is

' ξo

(II-4-26)

for uniform, smooth, impermeable slopes, where *ξ*o is the surf similarity parameter defined in Equation II-4-1.

Walton et al. (1989) modified Equation II-4-26 to extend the application to steep slopes by replacing tan *β*

in the surf similarity parameter, which becomes infinite as *β *approaches π/2, with sin *β*. The modified Hunt

formula was verified with laboratory data from Saville (1956) and Savage (1958) for slopes of 1/10 to

vertical.

(2) The nonbreaking upper limit of runup on a uniform slope is given by

Surf Zone Hydrodynamics

II-4-17

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