Multifractal approach to urban green spaces distribution in Est-Paris agglomeration (France) and potential benefits.

The growth of the world's population living in urban areas has led to change from natural to highly dense and impermeable landscapes. Moreover, the intensity and frequency increase of extreme events resulting from climate change (e.g. inundations, heat waves) produce a degradation of urban systems resilience capacity. The integration of nature-based solutions NbS in urban spaces has been widely accepted, like a sustainable strategy that allows to tackle these urban challenges while building resilience and improving well-being and health.

NbS are inspired by the nature, favouring natural processes in the cities like water infiltration or evapotranspiration (ET). Thanks to the latest, the vegetation shadow and wind dynamics favours air temperature reduction during heatwave events or mitigation of Urban Heat Island (UHI) phenomenon. Consequently, the distribution of urban green spaces might impact heat fluxes dynamics, by reducing temperature and its perception. They may also reduce virus spreads and also the sensitivity factors to them.

Following a spatial approach, this study aims to analyse the green space distribution across different scales in the agglomeration located in the east of Paris (France) and various scenarios of its development. To achieve this goal, the spatial simulation model "Fractalopolis" is used. This allows to generate fractal urban forms using an iterative downscaling scheme (IFS: Iterative Function System) applied to existing large scale patterns of green areas.

This work enables to analyse i) the access of population to the nearest green area and the fractal dimension of public urban green spaces; and ii) the impact of temperature reduction of different land-use scenarios by coupling a multifractal analysis of ET scaling behaviour measured at the local scale.