Architecture of the Roman Empire: Pont Du Gard

The Roman civil war to determine who would succeed Julius Caesar as ruler of Rome ended in the year 27BC. Victorious was Gaius Octavius, otherwise known as Octavian. He immediately assumed command of all military legions within the Empire and of the conquered provinces of the Mediterranean; Gaul, Spain, Egypt and Syria, before being proclaimed "senior consul in perpetuity" by the Roman Senate, and given the title "Augustus."

Augustus became the first Emperor of Rome, ruling from 27BC to 14AD. Under his rule, the Empire prospered far and wide, and wars were few and far between. The Roman economy flourished remarkably as a result of revenue reforms and building projects implemented during his reign. A large part of said building projects were the engineering of aqueducts throughout Italy and the wider reaches of the Empire. This included the Pont du Gard.

Designed primarily as a means of transporting water through a channel (specus) across the river Gard, the Pont du Gard is part of a 50km long aqueduct that transported water from springs near the town of Uzes to the city of Nimes in the Roman Colony, Nemausus. The aqueduct delivered an astonishing 20,000 cubic metres of fresh water to Nimes everyday. Its structural genius was the design of Marcus Agrippa, the adopted son-in-law of Augustus himself, and occurred during the height of Augustus' reign at around the year 19BC.

Engineers faced major problems when designing aqueducts such as the Pont du Gard. They had to ensure that the design allowed for water to flow steadily to its destination, using the only means they knew would propel it there: gravity. In the case of the Pont du Gard, the aqueduct was tailored so well in favour of the mechanics of gravity that the flow of every square centimetre of water was controlled steadily. The gradient of the aqueduct was so pedantically calculated that the level of the specus fell just 17 metres over the entire 50km distance.

In terms of the Pont du Gard itself, there were a couple of structural problems engineers had to overcome. To start with, the bridge section had to be both wide enough and high enough to conform to the gradient of the aqueduct. This was achieved by constructing three tiers of arches rising to the required 48.77 metres high and spanning the required 275 metres of the river valley. The bottom tier consisted of five cut-stone piers supporting six arches that established the foundation of the structure. It was a wide 6.36 metres to provide further strength for the foundation of the structure, as the second and third tiers were both narrower in width.

Secondly, engineers had to deal with the fact that the Pont du Gard spanned a river valley that was known to flood and flow quite vehemently at times. Winds also lashed the valley violently. It needed to withstand the flow of the river, and be tailored to survive floods and winds. Protection from the river was achieved firstly by add as triangular wedges to the bottom five piers so that the flow of the river would not be compromised by a pier blocking its path.

The arches on the bottom tier were also strengthened, and the central archway was widened from 15.54 metres to 24.52 metres so that it spanned the river entirely, allowing an increased flow of water to pass unhindered, reducing the effects of erosion caused by the flow of water. This is strengthened further by the placement of the piers on the second tier directly above those of the first, so that a bottom arch is not weakened by a second tier arch's base sitting atop its weakest point. This feature also helped to deal wit pressures imposed upon the structure by the wind, along with the fact that the arches themselves allowed for the wind to pass through quite harmlessly.

The Pont du Gard served its purpose as both a civic and a political utility. Firstly, it allowed for the transportation of water to one of Rome's most important provincial cities. In terms of civic benefits, this water filled drinking fountains and baths all throughout the city, keeping the population hydrated, clean, and generally quite happy. Politically, running water kept the populace both loyal and content in the idea of being a Roman Colony. It brought civilisation and the power of Rome to a place that had a history of being the home to the barbarian Gallic race, and united the people of Nimes to the centre of the Empire through their possession of the same urban facilities as Romans. This insulated Augustus and his successors in their popularity and power as Emperor, and helped to diminish chances of a rebellion against Roman rule.

The aqueduct also served to commemorate the achievements of Agrippa, who had commissioned the structure after being Governor of Gaul. Augustus was very fond of his son-in-law, Agrippa, and encouraged glorifications of him through successful feats in engineering. The Pont du Gard also served to help Romans who were away from home feel less resentful of time in the provinces through giving them the same facilities they would have been accustomed to in Rome itself.

The Pont du Gard was a magnificent success in Roman engineering. Often it is said that the Romans were masters in borrowing technology and perfecting it. This was certain a case of that trait in action. The adaption of the arch is among the many features that made for an extremely strong and durable structure which has stood the test of time against many adverse conditions. Its purpose as both a symbol of political power and civic service succeeded in making Roman rule and the memory of Agrippa last for as long as it did throughout Gaul. It is a truly epic success of Roman engineering.