The intensity and spatial variability of storm rainfalls play an essential role in occurrences of debris flows. Thus, understanding and characterizing the spatial variability of storm rainfalls is a prerequisite for debris flows mitigation. In this study, we investigate the spatial variabilities of rainfalls induced by different storm types using geostatistics. Summer convective storms are found to exhibit higher degree of rainfall spatial variability than typhoons, Mei-Yu and winter frontal systems. The semi-variogram of hourly rainfalls of convective storms was then used to assist in evaluation and augmentation of an existing raingauge network in Taipei.