The urban surface transformation process results both of urban control regulations (resulting from historical sanitary and highway policy) and of specific urban projects which affects strongly characteristics of the urban surface. The urban control regulations had specified, along the town history, a succession of morphological dispositions at the road and urban fabric scales as: interdiction of the front overhanging, streets alignment, material and texture prescriptions, widening streets and limitation of their heights, and giving density limits for different urban areas. Whereas the specific urban projects modified, in a known space and time, the relationship between the five ground surface types: natural, mineral, vegetal, built and water surfaces, by projects like: paving streets, opening new roads, filling rivers, or extension of built surface.
In order to observe the effects of these transformations on the urban microclimate at the Nantes city case, two simulation models are used: the SOLENE model, developed by the CERMA laboratory at Nantes, which implicates mainly the urban spaces but at a local level (block, square,…), and the "Town Energy Budget" (TEB) model, developed by the CNRM of Toulouse, that concerns the urban fabric and town scales. The first model tends to eclair us on the effects of the control regulations dispositions like alignments and limitation wide and height of roads, while the second model allows to observe the effects of surface transformation projects like rivers filling and ground mineralization.
Thus, the purpose of this presentation is to observe, through two urban examples of Nantes, the relationship between "morphological actions" and "microclimatic effects". A way for giving an "environmental" sense for the "diachronic" actions and regulations which have constituted successively the contemporary urban form.
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