Geology Reference
In-Depth Information
11
Use of GUEST Technology
to Parameterize a Physically-Based
Model for Assessing Soil Erodibility
and Evaluating Conservation
Practices in Tropical Steeplands
C.W. ROSE
1
, B. YU
2
, R.K. MISRA
3
, K. COUGHLAN
4
AND B. FENTIE
5
1
The Griffith School of Environment, Griffith University, Brisbane, Queensland, Australia
2
School of Engineering, Griffith University, Brisbane, Queensland, Australia
3
Faculty of Engineering and Surveying, University of Southern Queensland,
Toowoomba, Queensland, Australia
4
Annerley, Queensland, Australia
5
Queensland Department of Environment and Resource Management,
Queensland, Australia
11.1 Introduction
A general motivation that led to the develop-
ment of GUEST was to seek a more physically-
based soil erodibility measure than that provided
by the
K
factor in the USLE. This motivation
was strengthened by the finding that use of the
USLE methodology in the extensive wheat-
growing belt in Australia, where annual soil loss
is very variable, required several decades of
experimentation in order to determine the
K
fac-
tor with useful accuracy. This made the method-
ology inappropriate in such contexts (Edwards,
1987). Furthermore, the technique used to deter-
mine soil loss in establishing the USLE, thought
to be suspect, was later shown to lead to serious
underestimation of soil loss, especially in well-
structured soils (Ciesiolka
et al
., 2006).
A more specific motivation for the develop-
ment of GUEST was a recognition of the serious-
ness of both on-site and off-site consequences
associated with water erosion in tropical steep-
lands, both within Australia and in Australia's
neighbouring countries in southeast Asia. The
opportunity to develop a multi-country project to
There was more than one motivation that led to
the development of the closely related series of
computer-implemented mathematical models of
soil erosion known as the Griffith University
Erosion System Template (GUEST). The diction-
ary meaning of the word 'template' refers to a
guide or means of transferring a design. Choice of
this term indicates the original intent of the
model, namely to guide the analysis of data from
bare-soil runoff erosion plots so as to yield a
physically-based measure of the erodibility of the
soil. This elusive soil characteristic is sought, for
example, in the
K
factor of the Universal Soil
Loss Equation (USLE). The erosion behaviour of
bare soil plots is also commonly used as a base-
line against which erosion from alternative crop-
ping practices can be compared.
