During the last few decades, the urban hydrological cycle has been strongly modified by the built environment, resulting in fast runoff and increasing the risk of waterlogging. Nature-based solutions (NBSs), which apply green infrastructures, have been more and more widely considered as a sustainable approach for urban storm water management. However, the assessment of NBS performance still requires further modelling development because of hydrological modelling results strongly depend on the representation of the multiscale space variability of both the rainfall and the NBS distributions. Indeed, we initially argue this issue with the help of the multifractal intersection theorem. To illustrate the importance of this question, the spatial heterogeneous distributions of two series of NBS scenarios (porous pavement, rain garden, green roof, and combined) are quantified with the help of their fractal dimension. We point out the consequences of their estimates. Then, a fully distributed and physically based hydrological model (Multi-Hydro) was applied to consider the studied catchment and these NBS scenarios with a spatial resolution of 10 m. A total of two approaches for processing the rainfall data were considered for three rainfall events, namely gridded and catchment averaged. These simulations show that the impact of the spatial variability in rainfall on the uncertainty of peak flow of NBS scenarios ranges from about 8 % to 18 %, which is more significant than those of the total runoff volume. In addition, the spatial variability in the rainfall intensity at the largest rainfall peak responds almost linearly to the uncertainty of the peak flow of NBS scenarios. However, the hydrological responses of NBS scenarios are less affected by the spatial distribution of NBSs. Finally, the intersection of the spatial variability in rainfall and the spatial arrangement of NBSs produces a somewhat significant effect on the peak flow of green roof scenarios and the total runoff volume of combined scenarios.

The rapid urban growth followed by disordered occupation has been generating significant impacts on cities, bringing losses of an economic and social nature that directly interfere with the well-being of the population. In this work, a proposal for local urban infrastructure problems associated with watercourse management is presented, comparing Sustainable Drainage System (SuDS) techniques and Low-Impact Development (LID) concepts with alternative traditional interventions. The study addresses sustainable alternatives to cope with the urbanization of the Cehab’s open channel, which is an important urban watercourse tributary of the Muriaé River, at the municipality of Itaperuna, Rio de Janeiro—Brazil. The multi-criteria decision-making method called Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was applied here. The results highlighted the better performance of sustainable techniques when compared to the traditional ones, with an overall advantage of the geogrids and geocells for this case study. The obtained TOPSIS coefficients-C for these techniques were higher (0.59488, for Reach 1; and 0.68656, for Reach 2) than those for the others. This research, therefore, presented an important urban watercourse management methodology that can be further applied to guide sustainable investments and help the decision-making associated with the development of territories.

The high spatio-temporal variability of precipitation makes the hydrological responses of nature-based solutions (NBS) indeterminate. Hence, this study investigated the hydrological responses of a semi-urban catchment and three NBS scenarios concerning different spatio-temporal rainfall data from both C-band radar and X-band radar. Multi-Hydro, the fully-distributed and physically-based hydrological model, is employed to study the spatio-temporal rainfall variability and the resulting hydrological impacts on the NBS scenarios. The scale-independent indicator of maximum probable singularity (γ_s) within the Universal Multifractals (UM) framework is used to quantify the spatio-temporal variability of rainfall and catchment responses across scales. The main results show that the hydrological performances of the NBS scenarios can be largely underestimated or overestimated because of the spatio-temporal rainfall variability, with a relative error ranging from −91% to 199%, and NBS can effectively reduce surface runoff across scales, which is characterised by a lower γ_s.

Currently, Low Impact Development (LID) and Nature-Based Solutions (NBS) are widely accepted as sustainable approaches for urban stormwater management. However, their complex impacts depend on the urban environmental context as well as the small-scale heterogeneity, which need to be assessed by using the fully distributed hydrological model and high resolution data at small scale. In this paper, a case study (Guyancourt), located in the South-West of Paris, was explored. Three sets of high resolution X-band radar data were applied to investigate the impact of variability of spatial distribution of rainfall. High resolution geographic information has been processed to identify the suitable areas that can be covered by the LID/NBS practices, porous pavement, green roof, and rain garden. These individual practices, as well as the combination of the three, were implemented as scenarios in a fully distributed and physically-based Multi-Hydro model, which takes into consideration the variability of the whole catchment at 10 m scale. The performance of LID/NBS scenarios are analysed with two indicators (total runoff volume and peak discharge reduction), with regards to the hydrological response of the original catchment (baseline scenario). Results are analysed with considering the coupling effect of the variability of spatial distributions of rainfall and land uses. The performance of rain garden scenario is better than scenario of green roof and porous pavement. The most efficient scenario is the combination of the three practices that can reduce total runoff volume up to 51 % and peak discharge up to 53 % in the whole catchment, and the maximum values of the two indictors in three sub-catchments reach to 60 % and 61 % respectively. The results give credence that Multi-Hydro is a promising model for evaluating and quantifying the spatial variability of hydrological responses of LID/NBS practices, because of considering the heterogeneity of spatial distributions of precipitation and land uses. Potentially, it can guide the decision-making process of the design of LID/NBS practices in urban planning.

The standard method for characterizing the variability of overland flow focuses primarily on a single scale, usually the smallest scale available (i.e. the highest resolution). However, the extremes of overland flow are generally variable over a wide range of scales. Thus, the smallest scale has no specific hydrological significance, and a scale-independent characterization is more physically relevant. This study investigated the spatial variability of overland flows and evaluated the hydrological performance of the Nature-Based Solutions scenarios in terms of a possible improvement of the morphological functioning of the catchment at several scales.