- 造園雑誌 (ISSN:03877248)
- vol.38, no.4, pp.16-31, 1975-03-20
1. In defining an urban area, we can. take it as "a space occupied by artificial surfaces in a natural ecosystem,, which has originally existed but has been* partially destroyed by artificial structures resulting from human activities." Therefore, from the standpoint of physical planning, each urban area may be uniformly grasped as "an entity comprising two elements-natural surfaces and artificial surfaces." In other words, the form and shape of artificial surfaces occupying a certain space ( i. e., unit area) and the percentile ratio of the area occupied by artificial surfaces to the area of that space can be used as a planning index for that particular space. 2. Using Natural Surface-Artificial Surface (N-A) Formation Factor as a planning index, we have studied at this time to determine the limiting value of natural surfaces that are desirable in a unit area (or our daily life zone) measuring 90,000 sq. meters. This N-A formation factor may be expressed as follows : N-A Formation Factor (%) [numerical formula] Natural Surface Rate (%) = 100 - (N-A Formation Factor) 3. The study was made in the following manners : (1) The total area (11,727 hectares) of Takasaki City in Gunma Prefecture was divided into 1,303 meshes each measuring 90,000 sq. meters. Aerial photographs were taken for respective meshes and an N-A formation factor for each mesh was read by guess from such aerophotos. In this case, artificial surfaces comprised buildings, roads and the like. (2) N-A formation factors thus obtained (which ranged from O to 100%) were divided into 10 sections by an increment of 10% (i. e., 0-10%, 11-20%, 21-30%, …91-100%). Then, a survey was made at administrative areas within each of these sections to find out inhabitants' consciousness of satisfaction with natural environment (or their surrounding greens). The survey was conducted by the. use of a questionnaire which contained the following questions : I. Please reply to each of the following questions concerning your surrounding greens by selecting one of the following five answers : (i) Very-much. (ii) Comparatively less, (iii) Neither more nor less. (iv) Comparatively less, (v) Very little. A. How do you feel about your house or garden green? Ans. (i) (ii) (iii) (iv) (v) B. How do you feel about your neighbor's green? Ans. (i) (ii) (iii) (iv) (v) C. How do you feel about your town (or village) green? Ans. (i) (ii) (iii) (iv) (v) D. How do you feel about your city green? Ans. (i) (ii) (iii) (iv) (v) II. In the overall analysis of your living environment, how do you rate your living environment? E. Ans. (i) Excellent, (ii) Good, (iii) Fairly good, (iv) Bad. The above questionnaire was addressed to 1250 households randomly selected as subjects of the survey, 79.2% of which responded to the questionnaire. An analysis of those who replied to the questionnaire by age and sex has revealed that more than 85% of those who responded were of ages ranging from 30 to 69 and that the ratio of male respondents was 5 : 4. (3) Correlation charts for each of the above questions (as shown in Figures 5, 6 and 7) were prepared for analysis by combining N-A formation factors with inhabitants' responses to the consciousness of satisfaction with surrounding greens. (For the purpose of this analysis, the following plus and minus values were given to respective answers to Question I : (i) + 2, (ii) + 1, (iii)O, (iv)-1, and (v)-2. 4. The results of the study have indicated an extremely high correlation between N-A formation factors and inhabitants' responses to the consciousness of satisfaction with surrounding greens. For example, in Fig. 7 which is suggestive of a certain standard of our living environment, significant difference exists at a level of 0.1%, while Spearman's correlation coefficient shows -0.95. Also in Fig. 7, the N-A formation factor at the point of inflection from plus to minus value falls within the range of 50-60%. Judging from the results of this chart only, it can be concluded that natural surfaces in our living environment should be at least 40 to 50% of our daily life zone to satisfy ouy consciousness of green. These natural surfaces may consist not only of trees and woods, but also of the surface of water, dry river beds, bare lands, lawns, grasslands, paddy fields, farms and what not, irrespective of their private or public ownership. 5. The above-mentioned conclusion was solely based upon the method of determining the physical quantity of natural things (or naturals) to satisfy our consciousness of green vegetation as a human environment (Method 1). In addition, two other methods may be conceived of to determine this quantity. One concerns with a study of the efficacies or functions of green vegetation such as the stabilization of oxygen supply, the utilization of a green tract, of land, etc. (Method' 2) and the other,' with a study of the limit necessary to maintain a natural ecosystem which integrates both aboveground and underground spaces (Method 3). Although these two methods are now in the stage of finalization study and have questions yet to be solved, we have reviewed the results of this study by making a comparison with the results of trial calculations performed according to Methods 2 and 3, as will as with the results of similar studies by Method 1. As conclusions drawn from such review, we present the following for, discussion. (1) In case a daily life zone measuring 90,000 sq. meters is regarded as a unit area, natural surfaces should be secured up to a minimum of 40 percent of the unit area. (2) In the development of an urban area, artificial surfaces should be preferably held within 40 per cent of the total area intended for the urban area. (3) The percentile ratio of the area occupied by artificial surfaces in an urban area to the area occupied by natural surfaces in the same urban area should-normally be 50 to 50.