Dara Dam
Encyclopedia
The Dara Dam was a Roman
arch dam
at Dara
in Mesopotamia
(modern-day Turkey
), a rare pre-modern example of this dam type. The modern identification of its site is uncertain, but may rather point to a common gravity dam.
around 560 AD in his treatise on the architectural achievements of the Justinian I
era (De Aedificiis II.3). His report is notable for its clear understanding of arch action and the distribution of water pressure in arch dams; it provides the earliest description of such types of dam as opposed to the gravity dam, the standard design throughout antiquity
and beyond.
Procopius makes two essential points clear: first, the dam had a curved plan in order to withstand the water pressure, and did not follow a more or less curved line just because this was where the most solid bedrock was found, and secondly, the thrust of the water was not contained by the sheer weight of the structure (as in gravity dams), but transferred by the abutment
s to the wing walls of the gorge through the curvature of the lying arch
. Procopius writes:
Another ancient dam working by arch action was the Glanum Dam
in France
.
scholar Günther Garbrecht in the late 1980s has raised some doubts whether Procopius's account are to be interpreted as referring to an arch dam. Garbrecht was able to identify a dam site near the ancient city-walls whose characteristics were consistent with Procopius' precise description – with the exception of the crescent-shaped contour of the dam.
The discovered structure, a ca. 4 m wide and 5 m high masonry wall with a Roman concrete
core, had an estimated crest length of 180–190 m; its middle section was completely destroyed on a length of 60–70 m. Although it cannot be ruled out that the dam once followed a slightly curved course in the gap, the extant flanking walls rather indicate a polygonal ground plan. In this case, the Dara Dam would have resisted the water pressure by its sheer weight, not any arch action. Garbrecht surmises that the irregular shape of the dam may have led Procopius to a poetical allusion to the crescent-shaped firmament
. By his own admission, however, his observations in situ fell short of a systematic hydrological and topographical field survey
which he urged in view of the continuing deterioration of the ancient site.
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
arch dam
Arch dam
An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...
at Dara
Dara (Mesopotamia)
Dara or Daras was an important East Roman fortress city in northern Mesopotamia on the border with the Sassanid Empire. Because of its great strategic importance, it featured prominently in the Roman-Persian conflicts of the 6th century, with the famous Battle of Dara taking place before its walls...
in Mesopotamia
Mesopotamia
Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...
(modern-day Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
), a rare pre-modern example of this dam type. The modern identification of its site is uncertain, but may rather point to a common gravity dam.
Ancient account
The construction and design of the dam was related by the East Roman historian ProcopiusProcopius
Procopius of Caesarea was a prominent Byzantine scholar from Palestine. Accompanying the general Belisarius in the wars of the Emperor Justinian I, he became the principal historian of the 6th century, writing the Wars of Justinian, the Buildings of Justinian and the celebrated Secret History...
around 560 AD in his treatise on the architectural achievements of the Justinian I
Justinian I
Justinian I ; , ; 483– 13 or 14 November 565), commonly known as Justinian the Great, was Byzantine Emperor from 527 to 565. During his reign, Justinian sought to revive the Empire's greatness and reconquer the lost western half of the classical Roman Empire.One of the most important figures of...
era (De Aedificiis II.3). His report is notable for its clear understanding of arch action and the distribution of water pressure in arch dams; it provides the earliest description of such types of dam as opposed to the gravity dam, the standard design throughout antiquity
Ancient history
Ancient history is the study of the written past from the beginning of recorded human history to the Early Middle Ages. The span of recorded history is roughly 5,000 years, with Cuneiform script, the oldest discovered form of coherent writing, from the protoliterate period around the 30th century BC...
and beyond.
Procopius makes two essential points clear: first, the dam had a curved plan in order to withstand the water pressure, and did not follow a more or less curved line just because this was where the most solid bedrock was found, and secondly, the thrust of the water was not contained by the sheer weight of the structure (as in gravity dams), but transferred by the abutment
Abutment
An abutment is, generally, the point where two structures or objects meet. This word comes from the verb abut, which means adjoin or having common boundary. An abutment is an engineering term that describes a structure located at the ends of a bridge, where the bridge slab adjoins the approaching...
s to the wing walls of the gorge through the curvature of the lying arch
Arch
An arch is a structure that spans a space and supports a load. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.-Technical aspects:The...
. Procopius writes:
At a place about forty feet removed from the outer fortifications of the city, between the two cliffs between which the river runs, he constructed a barrier of proper thickness and height. The ends of this he so mortised into each of the two cliffs, that the water of the river could not possibly get by that point, even if it should come down very violently...This barrier was not built in a straight line, but was bent into the shape of a crescent, so that the curve, by lying against the current of the river, might be able to offer still more resistance to the force of the stream.
Another ancient dam working by arch action was the Glanum Dam
Glanum Dam
The Glanum Dam, also known as the Vallon de Baume dam, was a Roman arch dam built to supply water to the Roman town of Glanum, the remains of which stand outside the town of Saint-Rémy-de-Provence in south-west France. It was situated south of Glanum, in a gorge that cut into the hills of Les...
in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
.
Modern exploration
Field work on the ground by the GermanGermany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
scholar Günther Garbrecht in the late 1980s has raised some doubts whether Procopius's account are to be interpreted as referring to an arch dam. Garbrecht was able to identify a dam site near the ancient city-walls whose characteristics were consistent with Procopius' precise description – with the exception of the crescent-shaped contour of the dam.
The discovered structure, a ca. 4 m wide and 5 m high masonry wall with a Roman concrete
Roman concrete
Roman concrete was a material used in construction during the late Roman Republic through the whole history of the Roman Empire. Roman concrete was based on a hydraulic-setting cement with many material qualities similar to modern Portland cement...
core, had an estimated crest length of 180–190 m; its middle section was completely destroyed on a length of 60–70 m. Although it cannot be ruled out that the dam once followed a slightly curved course in the gap, the extant flanking walls rather indicate a polygonal ground plan. In this case, the Dara Dam would have resisted the water pressure by its sheer weight, not any arch action. Garbrecht surmises that the irregular shape of the dam may have led Procopius to a poetical allusion to the crescent-shaped firmament
Firmament
The firmament is the vault or expanse of the sky. According to Genesis, God created the firmament to separate the oceans from other waters above.-Etymology:...
. By his own admission, however, his observations in situ fell short of a systematic hydrological and topographical field survey
Archaeological field survey
Archaeological field survey is the method by which archaeologists search for archaeological sites and collect information about the location, distribution and organization of past human cultures across a large area...
which he urged in view of the continuing deterioration of the ancient site.