A Street Graph-Based Morphometric Characterization of Two Large Urban Areas

Luca Salvadori,Maria Grazia Badas,Annalisa Di Bernardino,Simone Ferrari,Giorgio Querzoli

doi:10.3390/su13031025

Luca Salvadori, Maria Grazia Badas + Show 3 more

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https://doi.org/10.3390/su13031025

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Abstract

Urban microclimate modelling, both numerical and in the laboratory, has strong implications in many relevant health and life-style management issues e.g., in studies for assessment and forecast of air quality (for both outdoor and, as boundary conditions, indoor investigations), for thermometric trend analysis in urban zones, in cultural heritage preservation, etc. Moreover, the study of urban microclimate modelling is largely promoted and encouraged by international institutions for its implication in human health protection. In the present work, we propose and discuss an adaptive street graph-based method aimed at automatically computing the geometrical parameters adopted in atmospheric turbulent flow modelling. This method has been applied to two real cases, the Italian cities of Rome and Cagliari, and its results has been compared with the ones from traditional methods based on regular grids. Results show that the proposed method leads to a more accurate determination of the urban canyon parameters (Canyon Aspect Ratio and Building Aspect Ratio) and morphometric parameters (Planar Area Index and Frontal Area Index) compared to traditional regular grid-based methods, at least for the tested cases. Further investigations on a larger number of different urban contexts are planned to thoroughly test and validate the proposed algorithm.

Highlights

As the target of this paper is to present and test a novel street graph-based grid method to automatically compute the geometrical parameters adopted in numerical and laboratory modelling of atmospheric turbulence, first of all, in this paragraph we present a list of the main parameters and symbols employed hereafter to describe the geometrical features of the urban areas
The method relies on an adaptive street graph-based morphometric characterization: starting from largely available datasets of building height data and a street graph, we show the possibility to derive specific morphometric values and, to potentially derive results on any area where data on building height are available
We prepare and pre-process an initial dataset: mainly, the building heights and, if available, the local street graph. For both Rome and Cagliari, building height data are available on open source sharing institutional sites, while street graph data can be obtained in the same platforms or through the OpenStreetMap service

Summary

Introduction

As the target of this paper is to present and test a novel street graph-based grid method to automatically compute the geometrical parameters adopted in numerical and laboratory modelling of atmospheric turbulence (and to compare it with previous method based on regular grids), first of all, in this paragraph we present a list of the main parameters and symbols employed hereafter to describe the geometrical features of the urban areas. As depicted, its total pertinence area (AT ) is shaded in green and its planimetric area (AP ) is shaded in orange. The red line denotes the width of a typical urban canyon (WC ) and the blue one indicates a building width (WB ). Assuming a wind direction (in the example NW, showed by the large blue arrow, U), it is possible to define the building width projected on a normal-to-the-wind plane (LB ), which is drawn in yellow in the figure.

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