In the process of tunnel excavation, irreversible ground subsidence is inevitable due to the soft nature of the overburden and due to possible lowering of the water table. The proposed tunnel is part of a railway connection between a railway line and a nearby seaport. To ensure the safety of underground and surface structures, ground settlement, horizontal displacements, horizontal strains and slopes were predicted prior to the tunnel excavation. A Finite Difference Method (FDM), viz. FLAC3D, which utilizes Fast Lagrangian Analysis of Continua in three dimensions, was selected to carry out a parametric study for predicting surface subsidence prediction. Elasto-plastic analysis in FLAC3D is found capable of simulating the behaviour of rock, soil, concrete lining and fluid adequately using a coupled stress-pore pressure model. A Parametric study was conducted in numerical simulation to estimate the effect of lag between excavation and supporting, overlying strata and the water table drawdown on the ground subsidence. The numerical modelling results indicated that an increase in lag between excavation and tunnel lining, as well as water table drawdown, exacerbated the subsidence occurrence. Surge in ground movements was observed among the eight boreholes (BH1 to BH8) drilled along the tunnel alignment; notably, the maximum vertical displacement was recorded at BH5, i.e., 2.6 cm. The subsidence and tensile strain profiles presumed that the effects of subsidence and strains extend up to a distance of about 70 m from the tunnel axis on both sides. This study provides comprehensive information for geotechnical engineers on how the water table drawdown affects the subsidence occurrence on the surface.