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Exceptional river gorge formation from unexceptional floods

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Antón López, Loreto and Mather, A.E. and Stokes, M. and Muñoz Martín, Alfonso (2015) Exceptional river gorge formation from unexceptional floods. Nature Communications, 6 (7963). pp. 1-11. ISSN 2041-1723

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Abstract

An understanding of rates and mechanisms of incision and knickpoint retreat in bedrock rivers is fundamental to perceptions of landscape response to external drivers, yet only sparse field data are available. Here we present eye witness accounts and quantitative surveys of rapid, amphitheatre-headed gorge formation in unweathered granite from the overtopping of a rock-cut dam spillway by small-moderate floods (B100–1,500m3 s�1). The amount of erosion demonstrates no relationship with flood magnitude or bedload availability. Instead, structural pattern of the bedrock through faults and joints appears to be the primary control on landscape change. These discontinuities facilitate rapid erosion (4270m headward retreat; B100m incision; and B160m widening over 6 years) principally through fluvial plucking and block topple. The example demonstrates the potential for extremely rapid transient bedrock erosion even when rocks are mechanically strong and flood discharges are moderate. These observations are relevant to perceived models of gorge formation and knickpoint retreat.


Item Type:Article
Uncontrolled Keywords:Earth sciences, Geology, Geophysics
Subjects:Sciences > Geology
Sciences > Geology > Geodynamics
ID Code:36551
Deposited On:21 Nov 2016 09:18
Last Modified:21 Nov 2016 09:23

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