Comment on Westaway & Bridgland (2010) - Causes, consequences and chronology of large-magnitude palaeoflows in Middle and Late Pleistocene river systems of northwest Europe

Westaway and Bridgland (2010) (W&B2010) present a palaeoflow estimation for the Channel River, partly based on calculations using input from the Busschers et al. (2007) Rhine-Meuse dataset. There are flaws in these calculations. W&B2010 calculate high-magnitude ‘bankfull’ palaeoflows (Qbf) for presumed critical periods within Marine Isotope Stage (MIS) 2 and MIS 6. To do so, geometric parameters were inferred from cored geological cross-sections, under the assumption that the source geometries represent former mega-scale channels, formed within critically brief periods. W&B2010 equate these assumed critically brief periods within MIS 2 to Heinrich Events 1 and 2 (HE1, HE2) and use individual OSL ages from our larger data-set to support this age correlation. This comment addresses: (1) Severe overestimations in the W&B2010 method of discharge calculations due to erroneous use of our channel-belt geometry as if it represented the wetted-channel perimeter, (2) Incomplete use of the Rhine-Meuse set of OSL dates in the process of correlating nested architectural elements to HE1 and HE2. Our comment points out that neither the architectural, nor the chronometric evidence from the Rhine-Meuse deposits supports the principal conclusion that during particular phases discharge reached values of several hundred thousand cubic meters per second. Instead, Rhine peak discharges were an order of magnitude smaller. This critically falsifies the inference that erosive records in downstream areas principally are the product of very high paleoflows generated by periglacial fluvial systems.