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Multiscale assessment of hydrological responses of Nature-Based Solutions to improve urban resilience

Abstract : Over the past decades, the urban hydrologic cycle has been greatly altered by the built environment, resulting in rapid runoff and an increased risk of waterlogging. Nature-based solutions (NBS), which apply green infrastructures, have been widely considered as sustainable approaches for urban stormwater management. However, as the urban environment is heterogeneous, the hydrological responses of NBS are still unclear. Therefore, the main objective of this thesis is to evaluate the performance of Nature-based Solutions using a fully distributed hydrological model Multi-Hydro to better manage stormwater in urban watersheds.The field analysed in the case study is a 5.2 km2 semi-urban catchment belonging to the Guyancourt city, which is located in the South-West suburb of Paris. Three types of rainfall data are used as rainfall inputs for different purposes. They are: (i) polarimetric X-band radar data of École des Ponts ParisTech (ENPC); (ii) the Météo-France polarimetric C-band radar data of Trappes; and (iii) the uniform rainfall by spatially averaging the X-band radar data at each time step. Three types of NBS are studied: permeable pavement, rain garden and green roof. Based on the properties of these NBS and catchment conditions, several groups of NBS scenarios characterised with different spatial distributions were created and investigated by using the fully-distributed and physical-based hydrological model Multi-Hydro.Since the hydrological responses of NBS sensitively depend on: (i) the spatial variability of rainfall; (ii) the spatial distributions of NBS; and (iii) their intersection effects, which implies that the overall performances of NBS scenarios simulated with uniform rainfall or lumped/semi-distributed model may not be entirely convincing. Thus, the first goal of this thesis is to investigate the uncertainty of hydrological responses in various NBS scenarios resulting from the spatial variability of rainfall and the heterogeneous distribution of NBS at the urban catchment scale. The results show that the uncertainty on peak flow of NBS scenarios was largely influenced by the spatial variability of rainfall, and the intersection effects produce a somewhat significant impact on the peak flow of green roof scenarios and the total runoff volume of combined scenarios.To further investigate the impacts of small scale rainfall variability on the hydrological responses of NBS scenarios, six different rainfall products from C-band radar and X-band radar are used as the rainfall inputs. The result indicates that the hydrological performances of NBS scenarios simulated with X-band radar data are more stable than that of the C-band radar data in terms of the studied rainfall events.To characterise the hydrological performance of NBS scenarios over a wide range of scales, the theoretical framework of Universal Multifractals (UM) was applied. In particular, the maximum probable singularity has been shown to be the scale independent indicator to effectively infer the critical extremes of overland flow, to optimize the intervention, increasing the city's resilience for stormwater management at multiple scales.Finally, the scale-independent cost-effectiveness indicator based on the UM framework has been developed and validated in comparison to the scale-independent one. It appears to be much more adapted to the multi-scale developments and, hence, more effective in supporting the future process of urban planning and decision-making.
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Submitted on : Tuesday, October 26, 2021 - 5:32:10 PM
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Yangzi Qiu. Multiscale assessment of hydrological responses of Nature-Based Solutions to improve urban resilience. Other. École des Ponts ParisTech, 2021. English. ⟨NNT : 2021ENPC0007⟩. ⟨tel-03404617⟩

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