TSUNAMI INUNDATION SIMULATION OF A BUILT-UP AREA USING EQUIVALENT RESISTANCE COEFFICIENT

Abstract

An equivalent resistance coefficient that includes the effect of drag caused by buildings as well as the bottom friction effect was investigated for two-dimensional inundation simulation of built-up areas with relatively coarse grids. In order to quantify the equivalent resistance coefficient for a given built-up area, we performed laboratory experiments and three-dimensional numerical experiments of steady and uniform flows influenced by square unsubmerged piers spaced at equal intervals in the longitudinal and transverse directions. The Manning's n, which represents the equivalent resistance coefficient, was evaluated by inputting experimental data into the Manning's equation. A semi-analytical formula for the n value under experimental conditions was derived via momentum analysis that included drag interaction effects. The n values resulting from laboratory experimental data, the three-dimensional numerical data, and the semi-analytical formula agreed well with each other. From these results, we found that the equivalent resistance coefficient n value is strongly dependent on the intervals between piers and increases according to water depth to the 2/3 power. In addition, as an application of the proposed n formula to the inundation model, we performed a simulation of a tsunami inundation on Imwon Harbor on the east coast of Korea.