Abstract
Topographic roughness is a popular yet ambiguous metric used in surface
process research for many applications that indicates something about
the variation of topography over specified measurement intervals. In
soil- and sediment-mantled settings topographic roughness may be framed
as a competition between roughening and smoothing processes. In many
cases, roughening processes may be specific eco-geo-hydromorphic events
like shrub deaths, tree uprooting, river avulsions, or impact craters.
The smoothing processes are all geomorphic processes that operate at
smaller scales and tend to drive a diffusive evolution of the surface.
In this article, we present a generalized theory that explains
topographic roughness as an emergent property of geomorphic systems
(semi-arid plains, forests, alluvial fans, heavily bombarded surfaces)
that are periodically shocked by an addition of roughness which
subsequently decays due to the action of all small scale, creep-like
processes. We demonstrate theory for the examples listed above, but also
illustrate that there is a continuum of topographic forms that the
roughening process may take on so that the theory is broadly applicable.
Furthermore, we demonstrate how our theory applies to any geomorphic
feature that can be described as a pit or mound, pit-mound couplet, or
mound-pit-mound complex.