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How is topographic simplicity maintained in ephemeral dryland channels?

Michael Bliss Singer and Katerina Michaelides
How is topographic simplicity maintained in ephemeral dryland channels?
Geology (Boulder) (October 2014) 42 (12): 1091-1094

Abstract

The lack of topographic complexity in ephemeral dryland channels, despite large variations in hydraulic controls and sediment texture, presents an unexplained paradox that limits understanding of their long-term evolution. In dryland basins, spatially and temporally discontinuous channel flow transports and sorts sediment along the bed intermittently and irregularly. The cumulative effect of these processes counterintuitively produces simple topography, manifest in straight longitudinal profiles and symmetrical cross sections, in contrast with perennial channels. This paper presents numerical modeling experiments based on field measurements to investigate dryland channel topographic development through the responses of bed-material flux and net sediment storage to variations in channel hydrology. We show that spatially variable flow creates and subsequently destroys incipient topography along ephemeral reaches, and that large flood events above a threshold overcome hydraulic and grainsize controls to dampen fluctuations in longitudinal sediment flux through a smoothing of the incipient channel bar forms. The results provide a physical explanation for emergent topographic simplicity in ephemeral dryland channels despite higher variability in streamflow and sedimentary characteristics compared to perennial systems.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 42
Serial Issue: 12
Title: How is topographic simplicity maintained in ephemeral dryland channels?
Affiliation: University of St. Andrews, Department of Earth and Environmental Sciences, St. Andrews, United Kingdom
Pages: 1091-1094
Published: 20141017
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 19
Accession Number: 2014-102342
Categories: GeomorphologySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2014373
Illustration Description: illus.
N36°00'00" - N43°45'00", W09°30'00" - E04°30'00"
Secondary Affiliation: University of Bristol, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201451
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