Streamlined erosional residuals and drumlins in central British Columbia, Canada

The upland–lowland pattern in the plateau region of central British Columbia, Canada forms an extremely large anastomosing channel network, with the uplands representing interfluves between channels. The study area landscape is remarkably similar in form to water-produced channel systems and qualitatively resembles flood landscapes from the Channelled Scablands and the margins of the Laurentide Ice Sheet. Numerical shape analysis of the area erosional residuals gives similar results as those derived from known flood landscapes; the length-to-width ratios of the uplands (L/W = 2.38, R2 = 0.89) are similar to those reported for braid bars and erosional residuals formed by glacial outburst floods. Thus, the study area landscape records a megaflood or floods that almost completely immersed the landscape.Drumlins with, in places, ubiquitous hairpin furrows, locations downstream from steep slopes facing into the flow, and eroded into till and bedrock similarly reflect regional-scale meltwater flow that immersed the landscape. The regional flow submerged the anastomosing channels at the time of drumlin formation. Drumlins likely formed as the anastomosing network developed; divergent drumlin orientations probably reflect either late flow or separate drumlin-forming events that did not appreciably alter the anastomosing system.

► Upland landforms identified as erosional residuals in anastomosing channel.
► Over 50,000 drumlins are mapped that occur on uplands and channel bottoms.
► Upland–lowland landscape resembles known catastrophic flood landscapes.
► Landscape–drumlin assemblage records terrain-immersing megaflood or floods.