عنوان مقاله [English]
Shade trees have many benefits in deferent dimensions; economic aspects (reduction of energy consumption in during hot period), physical aspects (maintenance utility) and social aspects (by increasing the vitality and efficiency of citizens) especially in cities facing with ‘temperature control issue’ in warmer months. Hence, this paper had directly emphasis on the size of the tree and its shade. In other words, the paper is discussed about ‘the shadows’ by inductive approach. Study goal is to measure the size of shade trees based on shape or volume (Canopy) of the trees to provide shade on the streets in central part of the city of Zabol. The city is located in the desert areas with low cloudy days and more sunshine hours. According to the surveys, per capita green space in the Zabol city is lower than national standards. The dominant species of eucalyptus and palm fan trees are in the streets of the city. The reason for selection of Zabol is exhausting heat in the most months of the year in the city. Overheating city of Zabol in different dimensions, has created a lot of problems. For example:
I) Economic aspects (increased energy consumption, increased use of cooling systems, etc.).
II) Physical dimensions (damage to urban infrastructure, environmental issues, reducing optimum standards of comfort and etc.).
III) Social aspects (reducing the amount of vitality and performance of citizens, reduce walking citizens, etc.). Hypotheses of this research were proposed as follows: The angle of the sun in July in the city of Zabol is vertical, if the crown is wide and flat. So in the most sidewalks there are tall trees with less shade to cover the entire surface of the pavement. Because the sun shines, shadow of object is farther away than it is, we have to select the tree species that is shorter in height. Theory and research records show that the issue and the problem of "shadow value in planning and urban design" has increased exponentially in recent decades; this issue is clear and objective and can be solved by paying attention to "the tree" and "the shadow "of the scientific calculation based on the angle of the sun (latitude cities surveyed) and the effect of tree shade done. This research is descriptive - applied based on a library studies, documents and surveys. The study area includes the center city of Zabol where two streets intersect each other in the market place. The sizes of the shadow of tall and umbrella shaped trees in July and in the hours that sun's heat is felt, are compared by using AutoCAD. of the sample is the city's central market which is nearly 36,000 square meters and located in the north eastern of ChareRah Shahrbani, Located in a zone where the number of corridors is. According to the existing experiences and the current state of this area, the research hypotheses are confirmed. Thus, according to the angle of the sun in July which is almost vertical for the city of Zabol, more shadow than its farthest thrown object can be applied, such as choosing tree species which are shorter in height. The "shadow" in different dimensions (physical, economic and social) for cities that are located in the arid climate, is vital, therefore, architects, planners, urban designers and urban planners do scientific works and several executive projects, but regarding to the scientific approaches, some of them have focused on the "volume (canopy) tree" and its "shadow" in urban areas. In some cities around the world, "shadow" has the annoying look (in the example of some European countries), however, "shadow" for hot and dry areas of the cities, particularly the city of Zabol, is vital so we should plan for several researches to find out different aspects to see and implemented. The results show that shadow should exist; amount of shadow in umbrella shaped trees is more than tall trees. In the 12 am the diameter shade of a palm tree is 3.22 m. while at the same time the shadow of the a Eucalyptus tree is 1.94 m.
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