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.




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 soil-mantled 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 quasi-dynamic model offers considerable improvement over the non-generalised quasi-dynamic model and the steady-state 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 steady-state models: relationship between cumulative frequencies FL(q) and FB(q).

The q variable represents return time for the Generalised QDM and QDM models, and critical rainfall for the steady-state model.

(Tarolli et al., 2008)





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.


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Montgomery, D. R., and W. E. Dietrich (1994). A physically based model for the topographic control on shallow landsliding, Water Resource Research, 30(4), 1153-1171.

Tarolli, P., Borga, M., Dalla Fontana, G. (2008). Analyzing the influence of upslope bedrock outcrops on shallow landsliding, Geomorphology, 93, 186-200,  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, 199-211, doi:10.1016/j.geomorph.2011.02.033