Slope distributions, threshold hillslopes, and steady-state topography

Authors
Citation
Dr. Montgomery, Slope distributions, threshold hillslopes, and steady-state topography, AM J SCI, 301(4-5), 2001, pp. 432-454
Citations number
88
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
AMERICAN JOURNAL OF SCIENCE
ISSN journal
0002-9599 → ACNP
Volume
301
Issue
4-5
Year of publication
2001
Pages
432 - 454
Database
ISI
SICI code
0002-9599(200104/05)301:4-5<432:SDTHAS>2.0.ZU;2-2
Abstract
Digital elevation models of two "steady-state" mountain ranges, the Olympic Mountains (OM) and Oregon Coast Range (OCR), are used to examine relations hips between slope distributions, the development of threshold hillslopes, and steady-state topography. Plots of drainage area versus slope for these mountain ranges exhibit substantial scatter that complicates comparison of range form to analytical theories and landscape evolution models. Contour p lots of the density of such data reveal an attractor at the scale of the tr ansition from hillslope processes to channel processes, and log-bin averagi ng reveals trends that parallel predictions of steady-state erosion laws bu t with different rate laws for five distinct process domains: hillslopes, v alley heads, and colluvial, bedrock, and alluvial valley segments. Slope hi stograms computed for 100 km(2) areas (defined by a 10 X 10 km grid) throug hout the OM exhibit approximately normal or exponential distributions in ar eas of active rock uplift and depositional topography, respectively. Local slope distributions in the OCR also tend to be normally distributed, but so me are left-skewed in areas with gentler slopes. Mean slopes determined bot h over the above referenced grid and a 10-km diam moving window are relativ ely invariant in the core of the OM in spite of strong contrasts in bedrock erodibility and gradients in long-term rock uplift rates. In contrast, the mean slopes in the OCR parallel latitudinal gradients in rock uplift rates and bedrock erodibility. Hence, the slope distributions in the OM and OCR reflect distinct relationships between development of threshold bedrock and soil-mantled hillslopes and steady-state topography.