Episodes of vertical accretion and catastrophic stripping: A model of disequilibrium flood-plain development

Research Article| December 01, 1986 Episodes of vertical accretion and catastrophic stripping: A model of disequilibrium flood-plain development GERALD C. NANSON GERALD C. NANSON 1Geography Department, University of Wollongong, P.O. Box 1144, Wollongong, New South Wales 2500, Australia Search for other works by this author on: GSW Google Scholar GSA Bulletin (1986) 97 (12): 1467–1475. https://doi.org/10.1130/0016-7606(1986)972.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation GERALD C. NANSON; Episodes of vertical accretion and catastrophic stripping: A model of disequilibrium flood-plain development. GSA Bulletin 1986;; 97 (12): 1467–1475. doi: https://doi.org/10.1130/0016-7606(1986)972.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract This paper describes flood plains formed episodically by vertical accretion along high-energy, laterally stable channels, in southeastern Australia. Overbank deposition gradually builds a flood plain of fine-textured alluvium over a period of hundreds or thousands of years, following which catastrophic erosion by a single large flood, or a series of more moderate floods, strips the flood plain to a basal lag deposit from which it slowly reforms. This periodic destruction appears due to the progressive development of large levee banks and flood-plain surfaces of highly variable relief. As the levees and flood plain grow, overbank flow is gradually displaced from the broad flood plain into the main channel and flood-plain backchannels, with a resulting concentration of erosional energy. Eventually, high flows greatly exceed erosional thresholds, and wholesale scour of the channel boundary and flood plain occurs. Vertical-accretion flood plains at different stages of development result in a wide range of bankfull recurrence intervals, even along the same river. Some of these flood plains are so infrequently flooded that they can be mistaken for terraces formed under a prior flow regime. The almost random but catastrophic nature of this flood-plain erosion means that sediment supply and transport are highly variable and probably impossible to predict. This model of flood-plain formation is seen as only part of a continuum of alluvial environments ranging from vestigial, coarsegrained, traction-load flood plains along high-energy rivers in narrow gorges to extensive low-gradient flood plains in which alluvial stratigraphy is dominated by fine-grained overbank deposition. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.