Original paper

An extreme drought in the year 69 AD on Lower Rhine A quantitative reconstruction

Roggenkamp, Thomas; Herget, Jürgen


Written documents represent the most comprehensive source of information on historical droughts. In Central Europe, written documents normally reach back only to medieval times. Exceptions are documents by historians from Roman times, writing of coeval events. Documents are partially preserved and content useful information on climate conditions in Roman times. One important historian was Tacitus, amongst others documenting events in 1 st Century AD at Lower Rhine in region of present day Germany and the Netherlands. In book 5 of "The History" Tacitus describes a battle between Roman troops and the Germanic tribe "Bataver" taking place in Rhine channel during a drought in the year 69 AD. Caused by low water depth, a Roman transport ship ran aground in the shallows and was attacked by the Bataver tribe. The location, mentioned by Tacitus, is near the Roman camp Gelduba, which is part of today's city of Krefeld in north-western Germany. On the basis of Tacitus' descriptions, add by archaeological findings, it is possible to reconstruct parameters to estimate the discharge during the drought. For estimating the cross-section area as well as the mean flow velocity, all needed parameters can be reconstructed. Estimated discharge is less than 300 m3/s, hence minor than minimal ever gauged discharge on Lower Rhine, which was 530 m3 /s in 1947. Recent mean discharge on Lower Rhine at the city of Krefeld is 2150 m3/s. River Rhine was an important roman transportation route as well as a naturally frontier to hostile Germanic tribes. Droughts impeded navigation and weakened the frontier. It seems that droughts caused more economic damage and social conflicts to Romans than flood events.


discharge reconstructionlower rhinedrought