Although now called the Liffey[i], in ancient times Dublin’s famous river was known by a different name, An Ruirthech. This loosely translates as ‘the stampeding one’[ii], a name which reflected the watercourse’s propensity to sudden floods of fast flowing water. This was a result of the river’s relatively short distance from source to the sea, which meant that heavy rainfall on the Wicklow mountains was quickly channelled downriver . This volatility was clearly illustrated in 765 AD, when an army of the men of Cianachta tried to cross the river at Dublin[iii]. Caught unawares, they were suddenly engulfed by raging waters and many were drowned.
These flash floods remained a hazard throughout the medieval and later periods, and there are many records of the city’s bridges being washed away in sudden deluges. Similarly, archaeologists have uncovered extensive evidence for Viking Age and Medieval flood defences, along both the southern and northern banks of River Liffey. These typically take the form of earthen banks and wooden revetments and were clearly an attempt to control the flow of the ‘stampeding’ Liffey. Indeed, the river remained susceptible to flash flooding right up until the last century, when the construction of hydro-dams on its upper reaches, helped to alleviate the problem.