Much progress has been made in extending the hydro-geomorphic
modelling toolbox as a result of developments in the field of digital
terrain analysis, also known as geomorphometry (Wilson and
Gallant, 2000; Pike, 2002). The enhancement of computer technologies
and the widespread availability of digital elevation models
(DEMs) since the early 1990s have impacted environmental
modelling greatly (Pike, 2000). Geographical information systems
(GISs) are now widely applied in hydrology and geomorphology
to automate basin, hillslope, and stream network analyses.
Several commercial GIS packages have incorporated more common
terrain attributes (e.g. slope, aspect, curvature, and wetness
index) and terrain analysis procedures (e.g. basin and stream network
extraction). These software packages are, however, often prohibitively
expensive. Furthermore, whilst commercial GIS packages
often contain basic terrain analysis capabilities, very few possess
the flexibility and advanced functionality needed by researchers.
Several terrain analysis packages have been developed for this
purpose, e.g. ANUDEM (Hutchinson, 1989), TARDEM/TauDEM
(Tarboton, 1997), LandSerf (Wood, 1998), TAPES (Moore et al.,
1991; Gallant and Wilson, 1996), LANDLORD (Florinsky et al.,
2002), and DiGeM (Conrad, 2002), some of which are freely available.
Unfortunately, many terrain analysis packages lack the visualization
and general spatial analysis capabilities of a GIS, or
have been developed as extensions to existing commercial software.
Additionally, although many terrain analysis packages possess
the advanced functionality needed by researchers, they are
often difficult to use and, therefore, remain inaccessible to nonexperts.
The Terrain Analysis System (TAS) was designed to meet the
research needs of government and academic scientists while being
simple enough in operation to be used for student instruction. TAS
is a stand-alone GIS that possesses much of the spatial analysis
functionality typically found in GIS packages. However, it is also
capable of advanced modelling of catchment processes. The following
is a brief description of TAS’s functionality for applications in
hydrology and geomorphology.