October 15, 2004


Design of Mechanisms for Urban Greening

* This article is under copyright protection.

Manabu Akaike
Universal Design Intelligence Inc.

In our cities, asphalt paving acts to keep temperatures from cooling down since water cannot accumulate in the soil, causing the heat of the day to continue to be emitted throughout the night, and together with high density energy consumption gives rise to the "heat island" syndrome, where air temperatures remain at higher than normal levels. As a result, a vicious circle is created wherein demand for air conditioning during summer months escalates and heat exhaust causes temperatures to rise even higher.

Various ways to accomplish urban greening have been tried in recent years as "heat island" countermeasures, with the primary aim of regulating carbon dioxide and nitrous oxide emissions. We can see many examples of experiments in urban greening, from planning for city parks to planting on the rooftops of office and apartment buildings. The development of technologies in the construction industry for the creation of artificial soil is making great contributions to urban greening efforts.

Around the Tokorozawa City railway station in Saitama Prefecture, an irrigation system has been installed to support the planting projects undertaken on the pedestrian walkways. Rainwater collected in cisterns that have been placed under the buildings that line the pedestrian walkway for the purpose of preventing floods in the city's rivers and streams is filtered by using direct solar powered pumps, and through the irrigation dripper (in-ground irrigation equipment) helps support the greening of the artificially created base.

The company that designed this irrigation system is Taisei Construction. Since the pump used is a direct flow low pressure pump of about 20-volts, there is no need for an AC transformer. Energy consumption is low, and not much space is required for the placement of the solar panels that power the pumps. The in-ground irrigation system ensures that even plants in direct sunlight will receive enough water.

Development of artificial soil for use in urban greening projects that incorporates high-molecular-weight organic substances with high water retention qualities is also on track, meaning that it may someday be possible to maintain urban plantings without irrigation systems. However, the benefits of having installed irrigation systems give rise to complex added value situations, such as the efficient use of rainwater collected in the indoor cisterns as drinking water in emergencies, filtering it using solar generated electricity.

Forestry Leisure Boom: Forestry as Sports

The concept of "smart growth" is popular in discussions of regional development leading toward a sustainable society. Smart growth means development that is fully rooted in the region, and a cessation of development that tends to overrun its periphery. We must engage in a full-fledged restoration of environments that have been ruined by overdevelopment, and even in cities, as far as possible we must create recycling systems that allow us to live in harmony with the natural environment.

In connection with efficient use of wood resources for forest reorigination, Taisei Construction is promoting active utilization of the diverse qualities of wood, such as use in wood pipes connecting outdoor facilities to public water systems and using trees and branches left on the ground after forest thinning projects as poles to support outdoor lighting, etc. For example, Taisei has obtained data that shows the amount of dioxins emitted during the construction process when using wooden street light poles versus steel pipe poles is about 44% lower. Taisei is advocating a variety of recycling systems that make use of resources that are close at hand, including making wood chips for paving by recycling branches pruned from fruit trees, building sub-floor heating systems that use heat exhaust from coal burning, and creating manmade nitrogen cycles by using composted garbage in urban produce gardens.

Lately, development of forest leisure activities as seen in the formation of volunteer groups for trimming trees has led to the use of discarded tree trimmings as light poles for the farm roads that local students use to commute to school, with ensuring safety a primary concern. After about five years have passed, those poles will be reduced to chips where they stand, to be finally returned to the soil as water and carbon gas. That is the grand design behind this recycling scheme.

The fact that ecologically responsible designs that are mindful of regional characteristics are beginning to emanate from some of the major general contractors that led Japan's high growth period deserves high marks.

JAPAN CLOSE-UP, October 2002, published by PHP

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