Typhoon-induced extreme water levels near Singapore

Abstract

Due to the diminishing Coriolis force towards the equator, the equatorial zone is known to be cyclone-free. However, on 27th December 2001, a tropical cyclone Vamei was formed near Singapore; 1.4 degrees latitude North from the equator, and made a landfall about 60 km northeast of Singapore. Although this event did not cause any major destruction to Singapore, the neighbouring areas such as states of Johor and Pahang of Malaysia had suffered inland flooding and landslide caused by the heavy precipitation of the storm. Chang et al. (2003) has suggested that the return frequency of a typhoon similar to Vamei is approximately 1 in 400 years, thus the possibility of a tropical storm occurring in Singapore could not be ignored. With the population density of over 7000 per square kilometer, the consequences of flooding due to storm surge can be devastating for Singapore. This study aims to provide a quantitative assessment to estimate the possible storm surge induced by typhoon near Singapore using numerical hydrodynamic modeling tool Delft3D. In order to simulate the hydrodynamic condition of both the tide and the storm surge in the Singapore Strait, the so-called Singapore Regional Model (SRM) will coupled offline with the cyclone model; Wind Enhanced Scheme (WES), both developed by Deltares|Delft Hydraulics (2004 and 2009b). The hindcast of the typhoon Vamei event has been attempted in this report to examine the applicability of the model in Singapore waters. Then the sensitivity of different typhoon’s tracks, forward speeds and radii of maximum winds on the storm surge will be examined closely to estimate the worst case scenario in terms of surge that could cause by a typhoon in this region. This report also acts as a preliminary study of the possible extreme high water levels which includes storm surge, tide and sea level anomaly that could occur along the coast of Singapore. According to the result of this study, the extreme event with an estimated return frequency of 1 in 400 years can cause the water level to reach as high as 2.0 to 2.8 depending on location.