نگرشی بر فعالیت‌های عمرانی ساسانیان در زمان شاپور اول در خوزستان (مطالعه موردی پل بندهای شوشتر و رامهرمز)

Introduction

Jareh Dam can be found 35 km Northwest of the Ramhormoz township in Khuzestan province, Iran; and has been constructed in narrow valleys within the Zard River by stones and plaster.  The Jareh bridge-dam is one of the largest Sassanian bridge-dam in the Khuzestan province. This study provides an understanding of the performance; the structure; the hydraulic mechanism of the Jareh bridge-dam and also the role played by it as a deterrent against the outbreak of the Zard River. 
 

Methodology

This study is based on the archaeology surveys ,excavations and library research . The main objectives of construction of new Jareh Dam was to supply irrigation water for Ramhormoz Plain, control floods and generate hydropower energy.  The purpose of this study was to collect all possible data and information, including field sampling, from the ancient Jareh bridge-dam and its surrounding structure before it was submerged and then analyze them. 
A research project in the area of the Jareh Dam was conducted; following the methodical surveys, a section of the Jareh village precinct was explored with a goal of reconstructing historical and cultural monuments .Other archaeological excavations have also been undertaken in the Ramhormoz plain in the Jare region and seven trenches were excavated in seven sites. Following the archeological excavations in Jareh Dam basin, several settlements mainly belonging to the prehistoric, historic, and Islamic eras were observed and recorded in the catchment area of the dam.   The architectural results suggested three residential phases. According to relative chronology, Phase 1 and 2 belonged to the Sassanian era, and the third phase belongs to the Islamic period. The main question was to find out whether the ancient Jareh bridge-dam is a Sassanid bridge or belonging to Islamic period?
The aim of the present paper is to report and introduce the ancient Jareh bridge-dam and its surrounding areas and functions, explain the method
 

Discussion

Although, accurately quantifying the time of construction seems complicated, but this age range (1370-2100 years) is reliable and include almost all the associated age uncertainty.  The upper limit of the estimated age of 1370-2100 years ago achieved by the MAM OSL Method may still overestimate the time of construction. Even when the minimum age model is applied, the ages of each single aliquot are still an average signal of many grains ranging from unbleached to fully bleached grains.  If the number of fully bleached grain in the aliquots is limited, the calculated ages can overestimate the true probable age.  The samples have been collected from the bottom of the reservoir deposit, upstream from the dam.  The date of the samples provides the time the dam was in use. In other word, it post-dates the time the dam was built. 
However, this age range (1370-2100 years) is historically consistent with the Sassanid period and Parthian period. Sassanid period ran from 224 to 651 AD (427 years) or 1368-1795 years ago.  The Parthians ruled from 247 BC to 224 AD.   Archaeological and historical information in addition to this age suggests that the ancient bridge of Jareh, was built in the Shapur I Kingdom period and or after the battle between the Shapur I and Valerian, as explained below.  
Shapur I (the first) also known as Shapur the Great, was the son of Ardashir, the founder of the Sasanian dynasty.   He was the second shahanshah (king of kings) of the Sasanian Empire.  Shapur I (240-270 AD), in the battle of Edessa in the year of 260 AD, successfully crossed the Euphrates River then went to the Antioch and seized the city. The Roman Emperor Valerian went to liberate the Antioch and took the city back, but then Shapur I strategically entrapped the Romans. Although the Romans tried to escape, they failed and the Roman Emperor was captured (Ball 2016). Consequently, Shapur I won in the war with Valerian. This victory is one of his most notable victories (Dignas & Winter, 2007).  The failed Valerian army, which consisted of seventy thousand soldiers, were captured by the Sasanian.  Shapur I used these captives for civilian activities in Iran (Ball 2016:23).   Among these captives, there were a lot of engineers and artists who were used for technical and engineering activities in the Fars and Khuzestan provinces (Dignas and Winter 2007). It is notable that in addition to numerous historical sources, in the inscription of the Ka'ba-ey Zartosht, the wars between Romans and Sassanid were discussed.   Tabari (1.827) specifically attests Roman prisoners of war being involved in dam construction. But it seems doubtful that Sasanian Persia relied exclusively on captured Romans to build its dams and bridges.  
The different methods Sassanid used to construct various buildings, especially dams, lead the dams of this period to be built with a mixture of both Persian and Roman techniques and style.  This resulted in the construction of the Sassanid bridge and dams on the Dez, Karkheh, Karun and other Rivers in Iran by the Roman captives (Howard-Johnston,2006 :201 & Adams 1962). Among them, the most notable are the Mizan dam (Potts 2012), the Shushtar bridge, Shadrvan dam (Huff 2010: 1083 & potts 2012), the Dezful bridge and the Gampou dam in the Larestan of Fars province (Malekzadeh 2013). However, there is no reason to believe that all Sasanian mortar structures date to the lifetime of the cited prisoners of war. Surely, Sasanian architects were quite capable of building such monuments without Roman help.  The bridge/dam at Gondeshapur is thought to be later (see the cited article by Huff with references). If little is known about this monument, there was also a bridge employing mortar on the Ghilghilchay Wall (Ancient West & East 5, 2006, 173) that is much later.  It is important to mention that none of these dams has been dated by an absolute dating method.  Admittedly, most Sasanian bridges and dams are not well dated – which is why this study is an important contribution.  Note, of course, also that the OSL dating allows for the Jareh bridge-dam to be later than Shapur I (or theoretically earlier).
The Jareh bridge Dam material and structure is somehow different to many other dams such as the ancient Gampoo dam; the ancient dams of Bahman, Amir, Mizan and Band-e Kaisar.  While the Jareh dam is only made by sand stones and mortar, the other dams are made by bricks or combination of sand stones and bricks.  However, most of them has been used as both dam and bridge.  Their dual-purpose design utilized a great influence on Iranian civil engineering and was instrumental in developing Sassanid water management techniques. The integration of a dam structure into bridge design became a standard practice of Iranian hydraulic engineering during and after Sassanian (Smith 1971).
 

Conclusion

Due to planning alterations of hydraulic infrastructure, we undertook a pre-flooding assessment of the new Jareh Dam’s impact on cultural heritage and recorded quantitative and multi-temporal data on archaeological sites before they are submerged. The archeological excavations in Jareh Dam basin indicated 3 residential phases.  Phases 1 and 2 belong to the Sassanid era and the third phase belongs to the Islamic period.  OSL dating ages (1370-2100 years ago) suggest that the ancient Jareh bridge dam was built during Sassanid period.  In fact, the Sassanians, after the formation of a powerful central government, made a lot of progress in the construction of dams and gates, of which the Jareh bridge is one of them; in order to meet the needs of residents in the field of irrigation and water supply, and also for the purpose of commuting residents of the area.