Unithydrograph techniques developed for design hydrographs in temperates wnes do not work well for arid zones. This is mainly attributed to the cellular nature of rainfall invalidating unit hydrograph theory. A technique is required that yields hydrograph shapes that are consistent with those measured in arid zones. A methodology has been developed that provides hydrograph shapes for catchment sizes ranging from 170 to 2672 km2. The method is based on analyses of 32 flood hydrographs in south west Saudi Arabia. The method, however, must be used concurrently with estimates of peak discharge obtained from regional studies.