Hightide - Floods in the Roman Empire

Floods in today's floodplain landscape, away from the built-up area, are certainly a picturesque spectacle. 

Natural disasters have accompanied mankind since time immemorial, and the Roman Empire was no exception. Floods in particular posed a constant threat, which placed a heavy burden on both the population and the urban infrastructure. For a long time, there was little evidence of preventative flood protection measures in historical sources. However, recent archaeological research shows that precautions were taken in ancient times to protect against the destructive consequences of flooding. Rivers and riverbanks played a central role in Roman times and were used by various population groups - traders, soldiers and farmers. However, this sometimes led to conflicts of interest with regard to flood protection.

Military town in Carnuntum in the third century, with the unregulated Danube in the foreground. (C) 7reasons

Roman protection measures included both technical and non-technical methods, including drainage systems, raised building plots and the construction of bridges - approaches that are similar to modern flood protection strategies. Different solutions were developed in different regions of the Roman Empire, as shown by Roman cadastral plans that already took flood risk into account. One example of this is the “cura riparum” (Latin for “bank care”), which regulated the protection and maintenance of riverbanks and dykes. These measures not only protected against flooding, but also regulated the course of the river. The “cura riparum” was therefore a legal and administrative obligation in the Roman Empire that dealt with the protection and maintenance of riverbanks.

In the foreground: Carnuntum's civilian town, behind it the military town and today's Pfaffenberg. Next to it the still unregulated Danube. (C) 7reasons

The city of Rome, which lay on the banks of the Tiber, was particularly affected by flooding. Its location between the seven hills favored regular flooding, as described in many ancient reports. Carnuntum, which was located on the south bank of the Danube, was also regularly confronted with floods in ancient times. The Danube played a crucial role for the city, both as an important trade route and as the natural border of the empire. Back then, however, the river was very different from today. Instead of a regulated river course, the Danube in ancient times was a branched, winding system with numerous side arms and marshy banks. For this reason, the Romans settled on raised river terraces to protect themselves from flooding. 

The past storms in 2024 in the Roman town of Carnuntum. Fortunately, no serious damage was caused despite the enormous volumes of water

In the north, the town bordered on dense riparian forests, while in the south the settlement area extended as far as the current route of the B9 federal highway. The topography of the banks of the Danube has changed constantly since ancient times. In Carnuntum too, the river repeatedly changed its course and shaped the vegetation through alluvial deposits and floods, which formed new river bends. The main stream of the Danube probably ran further north at that time. Parts of the legionary camp, which stood on the steep banks of the Danube, fell into the river over the centuries due to erosion. It was not until the river was regulated at the end of the 19th century that these landslides largely came to a halt.

In recent years, research into natural disasters and their protection in antiquity has become increasingly important. Historical and archaeological sources show that Roman societies not only reacted to acute disasters, but also prepared for the threat of flooding in the long term.

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Further reading:

J. Hettinger, Hochwasservorsorge im Römischen Reich. Praktiken und Paradigmen. Geographica historica 44 (Stuttgart 2022).