EVALUATION OF CHARACTERISTICS OF RUN-UP TSUNAMI NEAR COASTLINE BY ENERGY GRADE LINE ANALYSIS

Abstract

 In order to evaluate tsunami wave forces acting on land structures, it is necessary to know an inundation depth and a water depth coefficient of the tsunami. In the past, the value of 3 has been used as the water depth coefficient. However, based on the field survey after the 2011 off the Pacific coast of Tohoku Earthquake, it was found that the water depth coefficient can be reduced according to the distance between the land structure and its corresponding coastline.
 In this paper, we show that from research results in the past, the water depth coefficient is dependent on the Froude number. Next, we present a simple evaluation model based on the energy grade line method that can express the change of the Froude number from the information on the inundation depth in tsunami hazard maps. We conducted hydraulic model experiments in accordance with the Froude similarity law of the assumed scale 1/100, to confirm the validity of the evaluation model. Finally, we show the Froude number is reduced depending on the distance from the coastline and the elevation related to the land structure, and the ground roughness.