2.3 Sensitivity analysis for GALDIT parameters
The sensitivity analysis of GALDIT
parameters was used to verify the consistency of the analysis results in
the process of the vulnerability assessment (Saidi et al., 2013). To
minimize the error and uncertainty of the vulnerability index, Babiker
et al. (2005) and Saidi et al. (2011) adopted and evaluated appropriate
parameters by performing two methods of sensitivity analysis, that is,
the single parameter sensitivity analysis developed by Napolitano and
Fabbri (1996) and the map removal sensitivity analysis developed by
Lodwik et al. (1990). Since the development of the theoretical weights
of GALDIT parameters in 2001, the modification of ranges and weights of
vulnerability parameters of the GALDIT analysis method was continuously
attempted (Kazakis et al., 2018; Gorgij and Moghaddam, 2016). Among
these attempts, the sensitivity analysis of the parameters helps
determine the weights effectively by comparing with theoretical weights
in assessing the vulnerability with the score and weight of each index
(Gontara et al., 2016; Mahrez et al., 2018). The existing GALDIT has
determined parameters using averages for a long time. When calculating
the monthly SWI vulnerability index, the error and uncertainty of the
weights of the parameters must be minimized.
The single-parameter sensitivity analysis compares the “effective” or
“real” weight with the theoretical weight for the area in which the
index is assessed. The effective weight W (%) for the assessment area
of the GIS is calculated as follows (Babiker et al., 2005):