title: Catastrophic flooding origin of shelf valley systems in the English Channel.
abstract: Megaflood events involving sudden discharges of exceptionally large volumes of water are rare, but can significantly affect landscape evolution, continental-scale drainage patterns and climate change. It has been proposed that a significant flood event eroded a network of large ancient valleys on the floor of the English Channel-the narrow seaway between England and France. This hypothesis has remained untested through lack of direct evidence, and alternative non-catastrophist ideas have been entertained for valley formation. Here we analyse a new regional bathymetric map of part of the English Channel derived from high-resolution sonar data, which shows the morphology of the valley in unprecedented detail. We observe a large bedrock-floored valley that contains a distinct assemblage of landforms, including streamlined islands and longitudinal erosional grooves, which are indicative of large-scale subaerial erosion by high-magnitude water discharges. Our observations support the megaflood model, in which breaching of a rock dam at the Dover Strait instigated catastrophic drainage of a large pro-glacial lake in the southern North Sea basin. We suggest that megaflooding provides an explanation for the permanent isolation of Britain from mainland Europe during interglacial high-sea-level stands, and consequently for patterns of early human colonisation of Britain together with the large-scale reorganization of palaeodrainage in northwest Europe.
authors.affiliation: Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK. s.gupta@imperial.ac.uk
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Gupta
authors.forename: Jenny S
authors.initials: JS
authors.lastname: Collier
authors.forename: Andy
authors.initials: A
authors.lastname: Palmer-Felgate
authors.forename: Graeme
authors.initials: G
authors.lastname: Potter
mesh_terms: D004190:Disasters; D004739:England; D005843:Geography; D049690:History, Ancient; D006801:Humans; D009792:Oceans and Seas; D013997:Time Factors