Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Threshold phenomena in erosion driven by subsurface flow   We study channelization and slope destabilization driven by subsurface
(groundwater) flow in a laboratory experiment. The pressure of the water
entering the sandpile from below as well as the slope of the sandpile are
varied. We present quantitative understanding of the three modes of sediment
mobilization in this experiment: surface erosion, fluidization, and slumping.
The onset of erosion is controlled not only by shear stresses caused by
surfical flows, but also hydrodynamic stresses deriving from subsurface flows.
These additional forces require modification of the critical Shields criterion.
Whereas surface flows alone can mobilize surface grains only when the water
flux exceeds a threshold, subsurface flows cause this threshold to vanish at
slopes steeper than a critical angle substantially smaller than the maximum
angle of stability. Slopes above this critical angle are unstable to
channelization by any amount of fluid reaching the surface.

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The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
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The categories of this paper are: math
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ