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Theses

Deploying nature-based solutions in urban areas : thermal performance and urban feasibility across scales

Abstract : Rapid urbanisation rate and the modification of surface properties have altered energy balance and wind dynamics within the cities. This has modified locate climate, enhancing the Urban Heat Island (UHI). This phenomenon creates elevated temperatures are experienced in dense areas, mainly at night. Likewise, climate change could induce intensity and frequency of extreme events (such as heatwaves) are higher, becoming the UHI a challenge and threat of urban resilience. Nature-Based Solution (NBS), such as green roof, have appeared as a strategy for mitigation of elevated temperatures, because of the effect of evapotranspiration (ET) from vegetation. Nevertheless, the performance of NBS to cooling the air and its variability across different temporal and spatial scales are still unclear. As well, conditions that can influence their implementation in complex urban environments are unstudied.In this context, this thesis focuses on the evaluation of elements than could influence their installation across scales. First, campaigns of measure of the ET process were carried out in the Blue Green Wave (BGW), a green roof located in Bienvenüe building in front of the Ecole des Ponts ParisTech, in the Cité Descartes (eastern of Paris). The thermal and physical performance of the BGW was characterised through three different methods: the surface energy balance (SEB), the evapotranspiration chamber and the water balance during dry conditions. Differences in the three methods of measure were observed and the errors causing these were discussed. A sensitivity analysis served to determine principal variables affecting SEB estimations and make recommendations for further campaigns of measure.Second, the fractal geometry was used to analyse the complexity and heterogeneity of the spatial distribution in the case study of Est-Ensemble (eastern of Paris), and to develop a multiscale scenario of NBS deployment. More specifically, fractal dimension helped to analyse the hierarchical organisation of the built-up structure and NBS across different scales. These properties served in the multiscale scenario to reconcile the built-up structure with the NBS, by installing NBS of different sizes in the spaces not occupied by the buildings (lacunas) but over the fractal structure of buildings too.Finally, in order to improve the understanding of thermal flux variability measured in the BGW, statistical multiscale data analysis was used. The preliminary results demonstrated than air temperature and structure parameter of refraction index of air (〖C_n〗^2), impacting ET, exhibit a scaling behaviour affecting by intermittency, a commonly observed feature of turbulent flows. In addition, results suggested the need to investigate the additional meteorological parameters affecting turbulent activity in the BGW, such as wind speed
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Submitted on : Tuesday, August 30, 2022 - 4:21:11 PM
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Leydy Castellanos Diaz. Deploying nature-based solutions in urban areas : thermal performance and urban feasibility across scales. Environmental and Society. École des Ponts ParisTech, 2022. English. ⟨NNT : 2022ENPC0013⟩. ⟨tel-03764898⟩

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