توجه به باد در ساخت كالبد فيزيكي شهر زابل

Considering the Wind in Physical Shape of the City of Zabol

The city of Zabol is located in a low plain area in the eastern side of Iran. Distribution of pressure centres and the attributions of district topography are of those sorts that cause the formation of 120-days winds in Sistan. These winds originating from the mountains of eastern Afghanistan, circulating the Iran plateau from northwest and then enter the Sistan plain. The winds are called "120-days winds". Increase in their speed, will increase their climatological effects and then two different kinds of climates are formed in Zabol. In the years that the level of rainfall is high, current of 120-days winds carries the humidity and makes the air wet and delicate. In dry years when Hamoon lake is empty, the current of 120-days winds wipes the floor of the empty lake and carries the tiny particles of sand away, and pollutes the environment. In present study, the relations of characteristics of physical shape of the Zabul city as well as the major wind directions are surveyed. The results show that the streets which their directions are parallel with those of winds, chanellization effects of streets increase the speed of the winds and then cause undesirable effects. When the directions of streets are vertical to those of winds, circulation of air will happen. Then it will cause the accumulation of sand which results in environmental pollution. In this study some suggessions are made to decrease the negative effects of winds by changing the physical shape of the city.