This work presents two new indexes aiming to identify the effects of rainfall spatial variability on catchments hydrological responses. The proposed indexes are directly derived from rainfall intensity images and do not require any hydrological model. Their computation relies on a detailed analysis of spatial rainfall organization in function of flow distances to the catchment outlet. The efficiency of these two indexes has been tested herein, and compared to the two indexes formerly proposed by Zoccatelli et al. (2010, 2011). The tests presented rely on simulations. A simulation chain has provided an important case-study database including a large variety of rainfall events and catchments features. Two spatial rainfall resolutions were then considered (250 m x 250 m and the rainfall average over the catchment) in order to assess the impact of rainfall spatial variability on the catchments responses. Both situations were compared by computing the time and level differences between the peaks of simulated hydrographs. The computation of the different indexes finally showed that both sets of indexes relatively well explain the differences in peak times. However, the indexes proposed here seem to better explain the differences of magnitudes between the peaks.