Page 118 - Soil Degradation, Conservation and Remediation

106 4 Wind Erosion

Fig. 4.2 Wind erosion processes (Image source http://www.weru.ksu.edu/new_weru/images/
CreepSaltSusp.jpg)

latter depended on particle size and on the configuration and slope of the bed (Willetts
and Rice 1989; McEwan et al. 1992; Rice et al. 1995). With non-cohesive sand-sized
particulate surfaces, the saltating particles splashed up previously stationary grains.

4.3.2 Suspension

Suspension refers to the vertical uplift and horizontal transport of very small soil
particles that are generally removed from the local source area. Suspended particles
may end up on some meters or hundreds of kilometers downwind. They can range
in size from about 2 to 100 μm, with mass median diameter of about 50 μm in an
eroding field (Chepil 1957b; Gillette and Walker 1977). However, in long-distance
transport, particles <20 μm in diameter predominate because the larger particles have
significant sedimentation velocities (Gillette 1977). Some suspension-size particles
are present in the soil, but most are created by abrasive breakdown during erosion.
Because organic matter and some plant nutrients are usually associated with the finer
soil fractions, suspension samples are enriched in such constituents compared
with the bulk soil source. In the Great Plains, Hagen and Woodruff (1973) found that
the average dust storm lasted 6.6 h and estimated the median dust concentration to be
−3
4.83 mg m . Suspension movements are easily noticed as dust storms.

4.3.3 Surface Creep

Soil particles or aggregates of 500–1,000 μm diameter are too large to be lifted up in
normal erosive winds. They are pushed, rolled, and driven by the impacts of spinning
particles in saltation. In high winds, the whole surface appears to be creeping slowly