Geoscience Reference
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(a)
(b)
Figure 7.2 Inorganic soil surface seals, western NSW, Australia: (a) view across a low-gradient landscape where the soil surface
is generally covered with inorganic seal and scattered stones; (b) close-up of part of the foreground from A, showing depositional
seals along nonincised flow paths followed by overland flow.
larger and heavier drops to strike the ground. Addition-
ally, high rain rates (intensities) can arise in convective
storms, so that the bombardment of the soil can be par-
ticularly intense as a result of the combined effects of
large drops and high rain rates. Raindrop impacts are a
major driver of interrill soil erosion, but our concern here
is with their role in soil seal development. As remarked
above, the kinetic energy of falling raindrops is dissipated
in various kinds of deformation of the soil surface. In the
hypothetical 1 h storm, the power dissipated by the rain
of 100 mm/h, the power being dissipated rises to about
1.4 W/m 2 . These are not strikingly high values, but the
drops work on soil material that is subject at the same time
to other forces, such as those arising from the hydration
and swelling of clays, the escape of trapped air and so
on. Moreover, the soil surface is exposed to repeated rain
events and some of these are likely to contain short bursts
of very intense rain. The effects of intense bursts are not
well known, but it is possible that even though they may
last for just minutes, they are responsible for much of the
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