National Route E is a coastal road where overtopping waves cause frequent traffic disturbances. High waves resulting from a storm surge damaged the wave splash barrier for length of 78m out of 400m in October 2006. Impulsive wave pressure, acted on sections that were rendered incomplete due to scattering of wave-dissipating blocks as a result of the high waves and abnormal tide level, caused the damage of the wave splash barrier. The results of experiments revealed that the ratio of the critical wave force to the wave force acting on the barrier ranged from 2.6 to 3.0 in the damaged section, while the corresponding value in the undamaged section was 1.7 to 2.2