In this study high resolution precipitation data are used, derived from polarimetric X-band radar at 100 m, 1 min resolution. The data are used to study the impact of different space-time resolutions of rainfall input on urban hydrodynamic modelling response for 9 storms, in 7 urban catchments. The results show that hydrodynamic response behaviour was highly sensitive to variations in rainfall space-time resolution, more strongly so for changes in temporal than in spatial resolution. Under- and overestimations of flow peaks amounted to up to 100% with respect to the original 100 m, 1 minute rainfall input.