hierarchical system and spatial distribution of parthian sites in the sistan plain

in iranian archaeology, sistan played an important role especially in the parthian period. this region is well known since it was cross road for greeksto reach the east, a place for scythians arrival, the presence of powerful suren pahlav clan and the place of epic and heroic tales. during the parthian era favorable environmental conditions of sistan caused to arise many of towns and settlements in this region as from the total 1662 archaeological site discovered, 392 of which were assigned to be occupied by parthians. evidence of these settlements are scattered in the northern and especially southern half of sistan which are nowadays remain a depopulated desert. large parthian sites were identified in each of the two parts so that we regarded them as the central places according to their ranking in sistan. during this period of time, sistan was a prosperous land and it was populated due to the abundance of water resources and suitable arable lands. this paper tries to explore the impact of environmental factors in the parthian settlement patterns since our archaeological data derived from our fieldwork indicated that there has been a positive correlation between the environment and the sites occupation processes.