Microtopography of hillslopes and initiation of channels by Horton overland flow

Thomas Dunne, Kelin Whipple, Brian F. Aubry

Research output: Chapter in Book/Report/Conference proceedingChapter

11 Citations (Scopus)

Abstract

On long hillsides one can examine systematic downslope changes in the ground surface as Horton overland flow gathers into depressions and eventually incises the surface to form channels. Microtopography plays an important role in this process. We have sampled the microtopography of two long hillslopes in a savanna region of southern Kenya, and defined the spectral characteristics of its roughness at various distances from the drainage divide. The microtopography is fractal with a dimension that decreases systematically downslope, and the overall roughness varies between and along hillslopes in response to: (i) the weathering characteristics of the underlying bedrock; (ii) the type and density of patchy vegetation, and (iii) the tendency for wash to incise the surface with increasing intensity as runoff discharge increases downslope. The downslope decrease in fractal dimension reflects the progressive development of low-frequency roughness, here referred to as “swaley” microtopography, which the wash develops even far upslope of the channel head. The statistical analysis of surface roughness motivates a discussion of the role of microtopography in the interaction between wash and diffusive sediment transport processes that ultimately determines the critical distance from the divide at which channels begin.

Original languageEnglish (US)
Title of host publicationNatural and Anthropogenic Influences in Fluvial Geomorphology, 1995
PublisherBlackwell Publishing Ltd
Pages27-44
Number of pages18
Volume89
ISBN (Electronic)9781118664308
ISBN (Print)9780875900469
StatePublished - Jan 1 1995
Externally publishedYes

Publication series

NameGeophysical Monograph Series
Volume89
ISSN (Print)0065-8448
ISSN (Electronic)2328-8779

Fingerprint

microtopography
overland flow
hillslope
roughness
drainage
fractals
Kenya
sediment transport
weathering
bedrock
vegetation
statistical analysis
surface roughness
tendencies
low frequencies
transport process
savanna
runoff
interactions

ASJC Scopus subject areas

  • Geophysics

Cite this

Dunne, T., Whipple, K., & Aubry, B. F. (1995). Microtopography of hillslopes and initiation of channels by Horton overland flow. In Natural and Anthropogenic Influences in Fluvial Geomorphology, 1995 (Vol. 89, pp. 27-44). (Geophysical Monograph Series; Vol. 89). Blackwell Publishing Ltd.

Microtopography of hillslopes and initiation of channels by Horton overland flow. / Dunne, Thomas; Whipple, Kelin; Aubry, Brian F.

Natural and Anthropogenic Influences in Fluvial Geomorphology, 1995. Vol. 89 Blackwell Publishing Ltd, 1995. p. 27-44 (Geophysical Monograph Series; Vol. 89).

Research output: Chapter in Book/Report/Conference proceedingChapter

Dunne, T, Whipple, K & Aubry, BF 1995, Microtopography of hillslopes and initiation of channels by Horton overland flow. in Natural and Anthropogenic Influences in Fluvial Geomorphology, 1995. vol. 89, Geophysical Monograph Series, vol. 89, Blackwell Publishing Ltd, pp. 27-44.
Dunne T, Whipple K, Aubry BF. Microtopography of hillslopes and initiation of channels by Horton overland flow. In Natural and Anthropogenic Influences in Fluvial Geomorphology, 1995. Vol. 89. Blackwell Publishing Ltd. 1995. p. 27-44. (Geophysical Monograph Series).
Dunne, Thomas ; Whipple, Kelin ; Aubry, Brian F. / Microtopography of hillslopes and initiation of channels by Horton overland flow. Natural and Anthropogenic Influences in Fluvial Geomorphology, 1995. Vol. 89 Blackwell Publishing Ltd, 1995. pp. 27-44 (Geophysical Monograph Series).
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