Towards meeting the objective of simulating heat transfer processes in urban areas, the study of dispersion from a scalar (ground) surface area source has been addressed as a first step, since dispersion from such a source is in some ways analogous to heat transfer from the surface. Two different urban-like geometries are considered: an array with cubes of equal height and an array with random height cuboids. Some point measurement dispersion experiments in a wind tunnel have previously been carried out in identical arrays using a naphthalene sublimation technique. Large-eddy simulations (LES) of these experiments have been performed as a validation study and the details, presented here, demonstrate the influence of the roughness morphology on the dispersion processes and the power of LES for obtaining physically important scalar turbulent flux information.