城市綠帶之建築陰影對永續景觀設計的影響

The Influence of Building Shadows on the Urban Green Belt for Sustainable Landscape Design

Residents of high-density cities benefit from urban ecology and landscapes that incorporate green belts. A green-belt landscape can be both aesthetically pleasing and environmentally friendly, and makes use of energy-saving and sustainable materials. This study used the urban development that is taking place in the municipal area of Taichung of Central Taiwan as an empirical case to explore the impact of shadow from high-rise buildings on open spaces. The relative sunshine hours (RSH) of selected points in the cross-shaped green belt, in which trees are planted in rows, was simulated and calculated. The results show that the RSH differs according to location and season, which may affect the type of plants to be grown in a specific area. For example, an RSH of less than 30% was recorded over 21% of the green belt during the winter solstice. During the summer solstice, an RSH of more than 70% was recorded over 74% of the green belt. This may be too much sun for certain plants and public activities. We also monitored the RSH at selected measuring points of adjacent avenue. The RSH at these points varied from 7 to 96% during the summer solstice and 10 to 95% during the winter solstice. Our result s show that in a green belt the same types of plants may be subject to various natural light conditions. This study can help cities to design green belts that are visually appealing, sustainable, and cost effective. 城市綠帶不僅對生態和景觀影響極大，亦在人口擁擠的城市居民日常生活中扮演重要的角色。如何設計一個符合環境友善與節能永續兩方面需求的綠帶景觀，除了美學上的考量，更需要科學的判斷。本研究以位居台灣中部的台中市市政專區為實證案例，探討高層建築陰影對於開放空間的影響。研究中對十字形綠帶的相對日照時數（relative sunshine hours, RSH）進行了模擬和計算。結果表明，在冬至超過21%綠帶面積的RSH低於30%，此區域可能需選擇較為耐陰性的樹種以利其生長。而在夏至，超過74%綠帶面積的RSH則高於70%，這表示對某些植物和公共活動可能會產生暴露於過多陽光下的影響。其次，本研究在綠帶兩旁選擇行道樹測點對RSH進行了監測。這些林蔭道上相同樹種的測點RSH變化，在夏至為7~96%，而在冬至則為10~95%。因此，RSH會因地點和季節的不同而異，在綠帶中的植物受到建築物遮蔽各種自然光線條件的各種影響，而這會對特定區域預計栽種的植物類型生長產生顯著衝擊。藉由本研究可以提昇城市設計綠帶的視覺吸引力、永續性及成本效益之參考。