Today climate change is one of the most significant threats and global issues that should be concerned. It causes the increased number of natural disasters such as hurricanes, storms, typhoons and floods. Under these critical hydrological conditions, transportation infrastructure includes bridges easily got submerged, damaged and lead to its failures. Evaluation of bridge stability, hydrodynamic forces acted to bridges and understanding the complex flow behavior in particular during and after flooding plays an important role to estimate the probability of failure risks for existing bridges and optimal design of future bridges. In the present paper, the turbulent flow with high Reynolds number over a fully submerged bridge deck with various length-to-thickness ratios is numerically investigated by using ANSYS FLUENT. The blockage and submergence ratios are defined as 0.23 and 2, respectively. The realizable k–ε model and volume of fraction (VOF) is applied to predict the complex water surface profiles over the bridge deck and turbulence characteristics including backwater effect upstream of the bridge. Effects of the aspect ratio to the drag coefficient are studied.