Shimabuku, Nathan Takayuki2016-02-192016-02-192012-08http://hdl.handle.net/10125/101027M.S. University of Hawaii at Manoa 2012.Includes bibliographical references.In this thesis study, joint numerical and experimental studies were carried out to examine the effects that a submerged breakwater's length, distance from the beach and height have on the wave runup. The numerical program was based on a staggered grid leapfrog method on the shallow water equations which is used to simulate runup. Propagation over the reef is simulated with a predictor corrector Boussinesq scheme. We experimentally observed that a trend based on the wave's wavelength, length of the breakwater and lagoon spacing. We see that maximum and minimum runup reduction is observed at half integer and integer values of ζ and γ depending if the wave breaks. We define ζ and γ as the breakwater's lagoon spacing or the breakwater's length in terms of wavelength of the initial wave divided by the breakwater's height in terms of still water depth. We observed that the maximum runup reduction for a non breaking wave and minimum runup reduction for breaking waves were observed at half integer and integer values of γ. We also observed that if a breakwater is present the runup generated by waves can be reduced up to 40% but may be increased by 5%, with the exception of one measurement and that if wave breaking does occur the runup can be reduced by 80% and that it can be increased by 40%.engsubmerged reefbreakwaterThesis