The LES is first validated, and the importance of matching the Reynolds number of the simulations to real-world values is underscored. Analyses of the results show that the turbulent components of the transport of momentum and scalars within the canopy and roughness sublayers are found to be similar. However, strong dissimilarity is noted between the dispersive fluxes. The dispersive components are also found to be a significant fraction of the total fluxes within and below the roughness sublayer, and hence it is important to model their contribution correctly. Current Urban Canopy Models do not distinguish between these two components and thus new exchange schemes are needed in these models. Moreover, increasing frontal density induces a general transition in the flow from a rough boundary layer type to a mixed-layer-like type, which is found to have contrasting effects on momentum and scalar transport that also need to be accounted for.