FUNCTIONING OF GARKAZ EARTH DAM, GORGAN WALL AND ITS CHANNEL AS AN ANCIENT FLOOD DIVERSION PROJECT

摘要

There are remnants of a huge project which had been constructed 1500 years ago in thernnorth east of Iran. It contains a wall called Gorgan wall, an earth dam called Garkaz dam,rna ditch and channels. The related structures of the project belong to 5th century (or, at thernvery latest, early 6th century) A.D. This date coincides with a long lasting military conflictrnbetween the Sasanian Empire and the country on its north. Archeologists believe that thernaim of the wall was to protect the north-eastern borders of the Sasanian Empire, whichrndemonstrates the threat posed by its northern neighbors. They also believe that the mostrnimportant features of the Gorgan wall were its engineering systems, construction methodsrnand its water management in military systems. In this article the hydraulic functions of therndam, channel and ditch are investigated. The results of archeological studies, hydrologicalrndata of river and topographical information are used to estimate the flood and capacity ofrnchannels. Therefore, this complex was able to divert discharges less than 25 years returnrnperiod. Also, the ditch worked as consequent reservoirs to save the flood water along thernwall to prepare a defending channel. The Garkaz dam, Chaee Ghushan channel and ditchrnwere the flood diverting systems which were designed at very old time.