Forward scattering of continental shelf waves due to the presence of longshore topographic variations on scales comparable to those of the shelf waves is investigated. It is established that for variations for which distances from isobaths to the shore remain a fixed fraction of the local shelf width, no scattering could occur, even though the amplitude of such variation may be finite. Only deviations from shelf-similar depth profiles cause scattering which, for an exponentially deepening shelf, is likely to be limited to the lowest couple of shelf wave modes. The scattering gives rise to cross-shelf differences in the arrival time of flow events at points 'forward' from a topographic irregularity. The rate of this phase change (~1.5¿ km-1) for a topographic feature of moderate amplitude appears to be comparable to that observed.