「1924年アムステルダム国際都市計画会議」再考

東京緑地計画の環状緑地帯（1938年）のプロトタイプは決議３か?

抄録

 Peter Hall wrote, in the history of the green belt idea in Britain there have been several possible objectives of green belt policy: “one is pure containment: the idea of stopping towns growing any larger”(o₁, hereafter); “another is to give adequate access to the countryside for recreation of townspeople”(o₂, hereafter); and “a third is …to preserve agriculture and a rural way of life”(o₃, hereafter), while there are also several different forms of green belt: “at one extreme, a narrow green belt”(f₁, hereafter), and “at the other extreme, the countryside can be preserved in toto, with urban development allowed at intervals against a green background” (f₂, hereafter).

 In July 1924, the International Federation for Town and Country Planning and Garden Cities held an international town planning conference in Amsterdam and passed seven resolutions, the third of which said “it is desirable for the built-up parts of cities to be enclosed by green belts intended for, and to remain set apart for agriculture and horticulture, cattle breeding, etc. in order to prevent the formation of endless seas of houses”.

 In 1938, the Urban Planning Tokyo Local Committee proposed a plan of a narrow circular greenbelt of two kilometers wide (f₁) around the City of Tokyo “for the prevention of over-grown city” (o₁).

 After World War Two, some speculated that the prototype of the Tokyo Circular Green Belt was the third resolution of the Amsterdam conference. Thereafter, this view has been widely accepted in Japan. However, among the Japanese planners being involved in plan-making process of the Tokyo Circular Green Belt plan, only few people including Toitsu Takahashi at the Urban Planning Tokyo Local Committee, and Kouma Matsumura, the Planning Director of the Interior Ministry, referred to the third resolution. Saburo Kimura, who studied the history of London Green Belt Plan and was also involved in the Tokyo Circular Green Belt Plan, did not mention the third resolution at all. And the planner Kazumi Iinuma, who introduced the Amsterdam resolutions into Japan and repeatedly referred to them, did not present the third resolution as the prototype. The fundamental problem of this hypothesis is the lack of verification: it has not yet analyzed the background of the third resolution through the Amsterdam conference minutes.

 This paper refutes the prevailing view by analyzing the green belt ideas of Howard, Purdom, the conference resolutions, Unwin’s Greater London Regional Planning Committee’s report as well as those of the Japanese planners from the 1920s to the 1940s, and reaches the following conclusions:

 (1) The third resolution proposed not “a ring-like narrow green belt (f₁) to contain a large city (o₁)”, but the continuous agricultural areas against which garden cities would constantly multiply (f₂, o₃).

 (2) In the Greater London Regional Planning Committee’s Second Report in 1933, Unwin introduced a green girdle, or a narrow green belt (f₁) for containment (o₃) as well as the recreational use (o₂).

 (3) The Tokyo Circular Green Belt Plan was made with reference to Raymond Unwin’s Greater London Regional Planning Committee’s reports. Hence, the prototype was not the third resolution but Unwin’s report 1933.

 (4) Hajime Seki and Kazumi Iinuma, reading the conference minutes, got interested in preserving agricultural land as well as recreational space. They proposed the preservation of both lands by establishing a new zoning system.