Tree roots provide three stabilising functions: (a) reinforcement of the soil, (b) dissipation of excess pore pressures, (c) establishing sufficient matric suction to increase the shear strength. This paper looks at the way that vegetation influences soil moisture content distribution, and ground settlement. A theoretical model previously developed by the authors for the rate of tree root water uptake together with an associated numerical simulation is used in this study. Field measurements taken from literature published previously are compared with the authors' numerical model. The predicted results obtained from the numerical analysis, compared favourably with the field measurements, justifying the assumptions upon which the model was developed.