Encouraging urban greening is a key aim of the CSGN, as part of our A Place in Balance theme. Urban greening is fraught with technical difficulties when considering new urban areas or introducing green infrastructure into our existing town and cities. So we are delighted to report on the publication of two highly relevant guides and a piece of research:


CIRIA has produced C712: “The benefits of large species trees in urban landscapes: a costing, design and management guide”.

Trees have a unique contribution in the built environment by creating opportunities for biodiversity to flourish, whilst enhancing public amenity, providing space for local populations and allowing areas to function normally.

While all trees are beneficial to an urban environment, larger species are particularly significant as the most important single elements of urban green infrastructure. CIRIA’s review of research shows that large species trees convey the greatest financial, social and environmental benefits, and make a fundamental contribution to the well-being of almost 80 per cent of the UK population.

This guide aims to highlight the vital importance of large species trees, including the retention and enhancement of existing trees and carrying out of new plantings in streets, squares and parks for new and existing developments.

The guide can be purchased online.


The Environment Agency and Thames Water have supported the production of ‘Rain Garden Guide’.

This guide offers practical information on installing a small scale rain garden. For the purpose of this guide, a rain garden is a simple intervention designed to receive rain water from a downpipe or area of paving. The guide explains how drains can be overwhelmed by a sudden downpour and how this can cause flooding and affect water quality in local rivers. It illustrates how rain gardens can make a small but positive difference in addressing localised flooding and the quality of the local water environment. Alongside other sustainable drainage systems and actions to tackle diffuse pollution, rain gardens can be an effective part of a bigger solution.

The guide can be downloaded free of charge from the Rain Gardens website.

‘Effectiveness of Green Infrastructure for Improvement of Air Quality in Urban Street Canyons’, Environmental Science and Technology Journal, 17 July 2012

Street-level concentrations of nitrogen dioxide and particulate matter exceed public health standards in many cities, causing increased mortality and ill health. Previously, city-scale studies have suggested that the capacity for urban vegetation to ‘clean the air’ makes only a very modest improvement (<5%) to urban air quality. Few studies have taken full account of the interplay between urban form and vegetation, specifically the way pollution can be trapped in our densest, high rise developments which the authors refer to as ‘street canyons’.


This study shows that urban vegetation (trees, shrubs, green walls) in ‘street canyons’ can reduce street-level concentrations by as much as 40% for nitrogen dioxide and 60% for particulate matter. Substantial street-level air quality improvements can be gained through action in a single street ‘canyon’ or across city areas. Moreover, vegetation will continue to offer benefits in the reduction of pollution even if the traffic source is removed from city centres. Thus, the authors argue, judicious use of vegetation can create an efficient urban pollutant filter, yielding rapid and sustained improvements in street-level air quality in dense urban areas.

You can access this research published in Environmental Science and Technology Journal online.