From divots to swales: Hillslope sediment transport across divers length scales
Abstract
In soil-mantled steeplands, soil motions associated with creep, ravel, rain splash,
soil slips, tree throw, and rodent activity are patchy and intermittent and involve
widely varying travel distances. To describe the collective effect of these motions,
we formulate a nonlocal expression for the soil flux. This probabilistic formulation
involves upslope and downslope convolutions of land surface geometry to characterize
motions in both directions, notably accommodating the bidirectional dispersal of material
on gentle slopes as well as mostly downslope dispersal on steeper slopes, and it distinguishes
between the mobilization of soil material and the effect of surface slope in giving
a downslope bias to the dispersal of mobilized material. The formulation separates
dispersal associated with intermittent surface motions from the slower bulk behavior
associated with small-scale bioturbation and similar dilational processes operating
mostly within the soil column. With a uniform rate of mobilization of soil material,
the nearly parabolic form of a hillslope profile at steady state resembles a diffusive
behavior. With a slope-dependent rate of mobilization, the steady state hillslope
profile takes on a nonparabolic form where land surface elevation varies with downslope
distance x as x(a) with a similar to 3/2, consistent with field observations and where
the flux increases nonlinearly with increasing slope. The convolution description
of the soil flux, when substituted into a suitable expression of conservation, yields
a nonlinear Fokker-Planck equation and can be mapped to discrete particle models of
hillslope behavior and descriptions of soil-grain transport by rain splash as a stochastic
advection-dispersion process.
Type
Other articleSubject
soil productionfield evidence
evolution
diffusion
microtopography
bioturbation
distance
creep
geosciences, multidisciplinary
Permalink
https://hdl.handle.net/10161/3978Published Version (Please cite this version)
10.1029/2009JF001576Citation
Furbish,David Jon;Haff,Peter K.. 2010. From divots to swales: Hillslope sediment transport
across divers length scales. Journal of Geophysical Research-Earth Surface 115( ):
F03001-F03001.
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Peter K. Haff
Professor Emeritus
The neoenvironment is the total environment in which we live. It is the sum of the
natural, human, and technological systems and processes that surround us. It includes
for example forest ecosystems, animals and machines, nanotechnology, the internet,
highways, medical systems, power grids, human populations, political parties, governments
and bureaucracies, robots and religions and their interactions with each other. In
an age in which both the level and acceleration of techno

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