Growth of diamond has usually been discussed without invoking any form of surface diffusion. Our recent theoretical results identified, however, that bridging CH2 and CCH2 groups and radical vacancies can migrate on diamond {100} surfaces. The present work further explores migration of hydrogen atoms, bridging groups, and surface radicals, investigating the migration in two dimensions. The analysis is based on quantum-mechanical computations of potential energy barriers and vibrational frequencies, transition-state-theory evaluation of reaction rates, chemical-kinetic analysis of localized reaction networks, and idealized random-walk calculations of migration lengths. It is demonstrated that migration of hydrogen atoms and the bridging groups is nearly isotropic in two directions, along dimer rows and along dimer chains, while migration of surface radicals introduces distinct anisotropy to the overall character of surface diffusion. In their entirety, the results substantiate the governing role of surface migration in chemical vapor deposition of diamond.