Urban vegetation to combat noise pollution

Science topics April 2014 City

Benoît Gauvreau et Gwenaël Guillaume - AME Department, LAE Laboratory

From reducing heat islands to the impact of vegetation on noise

The growth of urban areas, which increases the size of artificially covered areas to the detriment of naturally covered ones, frequently has impacts on environmental quality, creating urban heat islands, atmospheric pollution, noise, etc. When it is technically feasible, the creation of green facades or roofs is a possible way of contributing to sustainable urban development.
From the purely acoustic standpoint, the effect of vegetation on urban noise environments can be considered at local, street, level, at the overall level of the city, with the district level between the two. The effects in question can be divided into two types for each of these spatial scales: direct effects (due to the absorbent properties of vegetation, particularly the substrate) and indirect effects (because they are responsible for changes in the movement of air and temperature gradients, which have an indirect impact on noise propagation). The effects in question have been measured in previous studies, in what is essentially a theoretical and numerical manner, for a limited number of spatial configurations and scales (some studies describe an experimental validation using a physical model and in situmeasurements).
Addition is required in this field in order to evaluate – numerically and experimentally – the influence of vegetation and the weather on urban noise environments, from the scale of the street to that of the district. Taking these new levels of complexity into account in the models developed by IFSTTAR requires development work to extend their scope of application.
The LAE has carried out this work mainly in the framework of the National Research Agency « VegDUD » project (2010-2014) which is managed by the IRSTV, in which the role of vegetation in sustainable urban development is analysed by an approach that combines climatology, hydrology, energy conservation and ambiances. The research in question has quantified the impact on the acoustic ambiance of these alternative practices for both private and public spaces, in particular by using classical physical indicators such as noise levels and reverberation times.

Cartographies des niveaux de pression sonore dans une rue sans et avec façades végétalisées (Ifsttar).

Cartographies des niveaux de pression sonore dans une rue, SANS (à gauche) et AVEC (à droite) façades végétalisées - Projet VegDUD (2010-2014).
Les niveaux de bruit sont représentés en couleur, du rouge (plus bruyant) au bleu (moins bruyant).


From urban noise reduction to the environmental description of districts

VegDUD project (2010-2014) - In-situ Measurements of acoustic properties of a vegetated cover (Ifsttar).The ANR « EUREQUA » project (2012-2016) does not merely study the influence of vegetation on urban ambiances, it also sets out to objectivise and evaluate the environmental quality of a district by identifying relevant criteria and observable factors.

These serve to characterise the physical environment (climate, acoustics, air quality), and are used by residents and users to evaluate the living environment.
These two cross-disciplinary projects bring together specialists from many fields (town planners, sociologists, psychologists, numerical analysts, etc.) and different research fields (meteorology, hydrology, acoustics, climatic comfort, pollution, etc.). The ultimate aim of the project is to evaluate the impact of various urban planning scenarios (introduction of vegetation into the urban fabric, regeneration of a district, modification of the road traffic network, etc.), working in collaboration with bodies such as (Météo-France, École Centrale de Nantes, CEREA, LAVUE, CERMA, IRSTV, LISST, LPED, etc.), This is part of a comprehensive systems-based approach that takes account of the behaviours of users (residents and visitors), and examines their relationship with the environment in a sensitive and socially aware manner (surveys, commentated routes, etc.).