Developing an urban heat island strategy
Cities like London, Tokyo and Stuttgart have strategies to reduce summer temperatures and cope with hot weather.
This helps to make city centres more sustainable in the long term and ensure that the need to moderate the urban heat island is understood and addressed at the heart of city planning and management.
The Greater London Authority has produced a document on London’s urban heat island that sets out options including cool roofs, green roofs, planting trees and vegetation, cool pavements, the sky view factor and heat wave detection and preparedness.
Other cities have employed different approaches. In Japan the city of Nagoya recently established a policy to require tree planting for all plots for new development over 300 sqm. Greenery must account for 10 to 20 percent of such a plot. Compliance with the rule is now a precondition for permission. In Tokyo the Metropolitan Government have identified a target to reduce the number of excessively hot summer evenings to 20 per year. To achieve this the City has used thermal mapping and is extensively monitoring ground conditions across the city. They are implementing a series of measures in those areas which suffer the greatest extremes.
One of the best examples of heat island management in the world is in Stuttgart.
Because of its location the German city has historically had problems with air quality. Climate-based planning has been carried out since 1938, with areas protected for unimpeded air flow to improve air quality and reduce the urban heat island. A series of wind paths have been designated across the city that allow cooler mountain air to flow into the heart of the city. No new building is allowed in an area designated as part of a wind path. In addition, the felling of trees of a certain size in inner city areas is banned, and as a result, greenery covers more than 60 percent of the city.
In Cities and Natural Process, Michael Hough argues that ‘on both a citywide and human scale, the parks and working landscapes within and surrounding Stuttgart are among the most climatically functional, socially useful and aesthetically pleasing of any modern city in the Western World’.
CABE and Urban Practitioners
with the cities of Birmingham, Bristol, Leeds, Liverpool, Manchester, Newcastle, Nottingham and Sheffield