Nature-based Solutions (NBS), a sustainable strategy for stormwater management, has been widely considered by many countries in the last few decades. NBSs are the actions inspired by, supported by, or copied from nature. In other words, they exploit the complexity of the laws of nature much more than conventional engineering solutions. However, this complexity includes the space-time variability of precipitation and the heterogeneity of urban systems, and a multi-scale understanding of the hydrological responses of NBSs is required to assess their performance, which remains beyond conventional hydrological techniques. We first argue that, in general, multifractals provide a convenient framework for dealing with this multi-scale variability. Second, we show that there is a need to develop a new multifractal indicator in the framework of Universal Mulifractals. Indeed, this new indicator can quantify the hydrological performances of NBS scenarios in terms of morphological changes of the field across scales. Finally, we test this indicator on the 5.2 km2 semi-urban catchment of Guyancourt, a town located south-west of Paris. This catchment undergoes a rapid urbanization process and is easily flooded in history. Here, the space-time rainfall data is obtained from the dual-polarimetric X-band radar of École des Ponts ParisTech (ENPC) with the spatio-temporal resolution of 250 m and 3.41 min. A moderate rainfall event that happened in 2015 is selected, and four NBS scenarios of porous pavement (PP), rain garden (RG), green roof (GR) and Combined (PP+RG+GR) are created based on the catchment conditions. Then, these NBS scenarios are simulated by the Multi-Hydro model (a fully distributed and physically based hydrological model developed by the lab HM&Co, ENPC) under the selected rainfall event. Overall, the new multifractal indicator is helpful to assess the hydrological performance of the NBS in terms of morphological changes (Fig. 1), which shows the RG and GR scenarios present a higher morphological variability than that of PP and Combined scenario, indicating the morphological variability in these two scenarios are more heterogeneous than that of PP and Combined. https://agu.confex.com/data/abstract/agu/fm21/2/4/Paper_880842_abstract_814117_0.jpg