I read that single-parameter sensitivity analysis and map removal sensitivity analysis are commonly used to assess the influence of parameters in DRASTIC and other index-based model. However, how do I actually do it? Because the output of DRASTIC is a raster with too many pixels trying to calculate for all pixels is an extremely huge task. Therefore, is there a software or way that I can do it efficiently? Can it carried out in ArcMap/ArcGIS? I've attached an example of an article that used sensitivity analysis for DRASTIC-LU model.
Use a univariate sensitivity analysis on the most sensitive or uncertain parameters. Vary them by + or – 25% and work out the ratios of output values :)
Andrew Paul McKenzie Pegman How do I vary them? Plus does uncertain parameters mean that the parameter is potentially don't have that much influence on the output? I still don't have a clear picture on how to do it.
Sensitivity analyses reveal how the model outputs change when more factors enter incrementally into a model, or when a single parameter is fixed while others vary, or when all parameters are fixed while one varies (i.e. univariate). A sensitive parameter is one that elicits a large change in model output for a small change in a given input parameter. The univariate sensitivity of model response (S) with respect to parameter x, is equal to the ratio of the relative change observed in the state variable y for a given relative change in the value x, with y being sensitive to x when S > c. 1, otherwise it is robust.
See: Hamby, D. M. (1994) A review of techniques for parameter sensitivity analysis of environmental models. Environmental Monitoring and Assessment 32: 135-154.
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