Here is an introduction to the story of Cork’s landscapes. Glimpses of the past. Amazing changes have occurred in the Lee valley since the last glaciation ended 11,600 years ago. Ice, river and estuary. Cork before Cork.
And then Cork. Archaeologists have discovered that, about nine hundered years ago, Hiberno-Norse people established the beginnings of the city by undertaking a major programme of land-claim, which consisted of filling the estuary with locally sourced silt. They began this task by diverting the South Channel and forming a new settlement near South Gate Bridge, as it is now.
The video shows the South Channel as it roars over South Gate Weir; the powerful flow was observed on February 25th, 2014 and includes water released by the ESB at the Inniscarra Dam after the prolonged wet weather of last winter (Donal Lehane, personal communication). The estimated discharge flow of about 70 m3/s could be considered to be representative of a typical river flood, of which there were probably many that swept down the South Channel during the medieval period; scouring mudbanks and undermining any timber structures that were in its path.
The image shows the residual flow in the North Channel at St Patrick’s Bridge on November 21st, 2009, one day after the infamous flood that caused extensive damage to the city. During the flood, a peak discharge flow of more than 800 m3/s is estimated. If such an extreme event had occurred in the eleventh or twelfth centuries, it seems unlikely that the early settlement of timber houses would have survived. Perhaps, earlier attempts to develop the wetland at Cork had already been postponed?