Simulation of coastal flooding during a typhoon event with the consideration of future sea-level rises in Tamsui River

摘要

Taiwan is an Island in the western Pacific Ocean and experienced morethan 3 typhoons in a year. During Typhoon periods, it always bringsintense rainfall, high waves, and storm surges, which often resulted incoastal flooding. The flooding can be aggravated by the sea level risedue to the global warming, which may subject Taiwan's coastal areas tomore serious damage in the future than the present. The objectives ofthis study are to investigate the flooding caused by typhoons in TamsuiRiver, a river located in the north of Taiwan by numerical simulations,considering the effects of sea-level rises according to the levelsuggested by the 5th Assessment Report of IPCC (IntergovernmentalPanel on Climate Change) for 2050 and 2100, respectively. Thesimulations were carried out by using MIKE21 HD (a hydrodynamicmodel) and MIKE21 SW (a spectral wave model). Our preliminaryresults showed that with only the effect of rainwater discharge, themaximum surface level of the river during the storm near the estuary islower than the river level during the storm surge condition. With thestorm surge and sea-level rise, the maximum river levels near theestuary were 3.4～3.9 m. When the flow rate increases upstream of theGuandu Bridge, the water level can be found near the mouth of theTamsui significantly raising the average water level is about 3.7 ～ 4.3m.This showed that due to higher sea-level, the area near the estuary willbe flooded.