The influence of aggradation rate on braided alluvial architecture: field study and physical scale modelling of the Ashburton gravels, Canterbury Plains, New Zealand

Philip Ashworth, J.L. Best, J. Peakall, J.A. Lorsong

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNChapter

Abstract

Theoretical process-based models of braided alluvial architecture suggest that aggradation rate is a primary controlon the geometry, stacking and heterogeneity of sedimentary deposits. This hypothesis is tested at the scale of thechannel and bar using a combined field and flume modelling study, which quantifies the impact of a change inaggradation rate on the frequency of occurrence and geometry of the key depositional units that dominate coarsegrained,braided alluvial architecture. Aggradation of a 1 : 50 scale model of the braided Ashburton River, NewZealand, produces realistic alluvial architecture that closely corresponds to 7 km of logged field prototype outcrop.A twofold change in aggradation rate in the flume model and an order-of-magnitude change in the field outcrop,have no influence on the geometry and vertical distribution of fine- and coarse-grained depositional niches.Braided alluvial architecture at the channel scale therefore is determined by the local ‘instantaneous’ aggradationrate, related to individual flood events, rather than the long-term, regional aggradation rate.
Original languageEnglish
Title of host publicationFluvial Sedimentology VI
EditorsN.D. Smith, J. Roger
Place of PublicationUK
PublisherBlackwell Science
Pages333-346
Number of pages14
ISBN (Print)9780632053544
Publication statusPublished - 1 Jan 1999

Publication series

NameSpecial Publication of International Association of Sedimentologists

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