The chirality of magnetostatic Damon-Eshbach (DE) magnons affects the transport of energy and angular momentum at the surface of magnetic films and spheres. We calculate the surface-disorder-limited dephasing and transport lifetimes of surface modes of sufficiently thick high-quality ferromagnetic films such as yttrium iron garnet. Surface magnons are not protected by chirality, but interact strongly with smooth surface roughness. Nevertheless, for long-range disorder, the transport is much less affected by the suppressed backscattering (vertex correction). Moreover, in the presence of roughness, ferromagnetic resonance under a uniform microwave field can generate a considerable number of surface magnons.