||This research adopted CMCOT model (Cornell Multi-grid Coupled Tsunami Model) to simulate the wave ran up as the tsunami entered the shoaling water of coastlines, the inundation range on land, and the bridge scour caused by tsunami as it made its way upstream in the rivers.|
The inundation range was estimated with the fault parameters of Manila Trench and a simulation of bell-sphaped curve waves. The result indicated that if the height of bell-sphaped curve was the same as the maximum water level of the tsunami passed to Kaohsiung offshore, the inundation rage was generally consistent. In the simulation of different water level, we discovered that one meter of wave height was sufficient to inundate the entire coastland of Qijin and Gushan District and that the inundation rage would expand as the wave height increased. With the maximum simulated wave height of six meters, the inundation rage included Gushan, Qijin, Yancheng, Qianjin (small scope), Qianzhen, Fengshan, and Xiaogang District. As to the comparison of historical tsunami, according to the particle size analysis of geological survey from the Kaohsiung Mass Rapid Transit, a layer of fine sediment could be found at specific depth, and its particle size (about 8ψ) was significantly different than that of other layers. If this fine sediment was the border of tsunami sediment, the height of historical tsunami wave could be 4.9 meters.
With regard to bridge scour, Gwando Bridge was chosen as research area. The result from the sediment simulation of COMCOT model was similar to the scour hole and sediment deposition formed by horseshoe vortex system. Based on the result, the scouring and depositing processes were mainly influenced by the particle size of the sediment. In the simulation, the results of different sediment particle sizes were as follows:
(1) If the particle size of sediment was greater than 62μm, the maximum scour depth was less than 4 cm, and the maximum height of deposition was under 3 cm.
(2) If the particle size of sediment was between 4 and 62μm, the maximum scour depth was between 4 and 5 cm, and the maximum height of deposition was between 3 and 4 cm.
(3) If the particle size of sediment was smaller than 4μm, the maximum scour depth was above 6.8 cm, and the maximum height of deposition was greater than 5 cm.