| Summary: | 博士 === 國立成功大學 === 建築學系碩博士班 === 90 === The urban environment nowadays is consisted of impermeable materials. This high percentage of impervious area (Imp) not only causes the phenomenon of urban runoff, but also brings about high temperature in urban and destroys the urban ecology.
This research builds up an investigation method by sampling from different zonings of Taipei and Tainan and tries to use the Imp to evaluate the current Performance of Soil Water Retention. The results conducted by the investigation shows that the Imp of each zonings in are, 86%, 84% for residential area, 100% for commercial area, 92%, 90% for industrial area, 36%, 19% for park area, 68%, 60% for educational facilities area and 91%, 78% for government organization area. The values are much lower than the data listed in pervious documents in Taiwan and also lower than some parts in Japanese city that are equally developed as Taipei and Tainan.
To realize the relation between the “index of soil water retention in building site”, “percentage of impervious area (Imp)” and runoff phenomena in urban area, we take Huweiliao, a part of Tainan city, for example to proceed the of urbane runoff experiment. During 9 rain events from the experiment, the coefficient of runoff is 0.405 after calculation. Dealing with the previous data experimented by Wen, the relation between Imp and coefficient of runoff is 0.87, and the relation between “index of soil water retention in building site” and coefficient of runoff is 0.88, higher than Imp (P<0.05). Further more, we apply the result in a developed residential area, we find that if the previously development higher than the standard of “index of soil water retention in building site”, runoff volume could reduce about 21.3%.
So the government develop the assessment of soil water retention in building site to be one of the assessment of green building, using infiltration, storage, retention and landscape engineering to increase the capability of water storage of soil in building site. This research prove that the “index of soil water retention in building site” can help to reduce the runoff volume in urban area, and it could also provide the government to control the Imp in the city by law.
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