EXPERIMENTAL STUDY ON THE ENERGY REDUCTION OF A SOLITARY WAVE USING A SAND DUNE-COASTAL LAGOON SYSTEM

Abstract

 Laboratory experiments were conducted to understand how a tsunami-like solitary wave energy can be reduced in one horizontal dimension against the effects of beach slope, sand dune height, depth and length of the lagoon in cross-shore direction. The wave height to depth ratio from 0.1 to 0.4 was used. The resultant wave transmission height and maximum runup for beach slope of 1/30 and 1/7 were measured using a slope of 1/4 at landward of the lagoon. The dimensional analysis was used to pick up important parameters for comparing the maximum runup effect. The plunging breaking, surging breaking and nonbreaking type of waves were observed on the beach slope. The undulations with no breaking, leading wave breaking and turbulent bores were observed inside lagoon with the change of wave transmission height to lagoon depth ratios. Thus, a coastal lagoon having gentle beach slope, larger sand dune and larger length in cross-shore distance helps to increase more resilience against tsunami attack.