

GQDM (Generalized Quasi Dynamic slope stability
Model) This program is free software. This program is
distributed in the hope that it will be useful, but without any warranty; without
even the implied warranty of merchantability or fitness for a particular
purpose. Overview GQDM is a suite of programs for slope stability
mapping under the generalized quasi dynamic wetness index (GQDWI) assumptions
(Tarolli et al., 2008; Tarolli
et al., 2011), and for the prediction of both topographic and climatic
control on shallow landslide initiation processes in hilly mountainous
terrain. The GQDWI describes the runoff propagation on bare rock surfaces (or
other kind of soils) connected to downslope soilmantled topographic
elements. This approach yields a simple enhanced model capable of describing
the influence of upslope bedrock outcrops (or other kind of soil layer) on
the pattern of downslope soil saturation. The model develops upon a theory
for coupled shallow subsurface flow and landsliding
of the soil mantle previously proposed by Montgomery
and Dietrich (1994). The model uses a ‘generalized quasidynamic’
wetness index to predict the spatial distribution of soil saturation in response
to a rainfall of specified duration for different kind of soils. The rainfall
predicted to cause instability in each topographic element is characterised by duration and frequency of occurrence.
The incorporation of a rainfall frequency–duration relationship into
assessment of landslide hazard provides a practical way to include climate
information into estimation of the relative potential for shallow landsliding. It is revealed that the generalised
quasidynamic model offers considerable improvement over the nongeneralised quasidynamic model and the steadystate
model in predicting existing landslides as represented in the considered
landslide inventory. A clear example of its performances is showed in the
Figure 1. The figure shows that, for a given percentage of basin area with
index values less than the threshold, many more observed landslides fall in
the area described by the GQDM with respect to the other two models. Figure 1. Comparison of Generalised QDM, QDM,
and steadystate models: relationship between cumulative frequencies F_{L}(q) and F_{B}(q). The q variable represents return time for the Generalised
QDM and QDM models, and critical rainfall for the steadystate model. (Tarolli et al., 2008) Modules timedrain.exe: module for the calculation of the effective contributing area at
different drainage durations. The module takes into consideration the rocks
code, the soil code, the saturated hydraulic conductivity K (LT^{1})
and the soil effective porosity e (). This module needs the
input setting files command.tdr.
For the evaluation of critical rainfall or return time of critical rainfall
you can use the other modules available in the software packages page: SSM
and TRGQDM. Download: please send an email to paolo.tarolli@unipd.it References Montgomery,
D. R., and W. E. Dietrich (1994). A physically based model for the
topographic control on shallow landsliding, Water
Resource Research, 30(4), 11531171. Tarolli,
P., Borga, M., Dalla Fontana, G. (2008). Analyzing the influence of upslope bedrock outcrops on shallow landsliding, Geomorphology,
93, 186200,
doi:10.1016/j.geomorph.2007.02.017. Tarolli,
P., Borga, M., Chang, K.T., Chiang, S.H. (2011). Modeling shallow landsliding susceptibility
by incorporating heavy rainfall statistical properties, Geomorphology, 133, 199211, doi:10.1016/j.geomorph.2011.02.033 
