3.4 Single parameter sensitivity analysis for Monthly GALDIT index using effective weight
The effective weight was calculated for sensitivity analysis, as summarized in Table 3. According to Babiker et al. (2005), the weight used for vulnerability assessment can vary according to the study area. The ‘effective weight’ represents the weight that is actually applied to assess the vulnerability index. As a result of the sensitivity analysis, the index with the largest effective weight was T. Note that an average value of 8 to 9 was assigned to the parameter value of T in the process of applying the modified GALDIT method for hydrogeological data in the previous section. The ratio of the effective weight of T was high, owing to the parameter value that was calculated to be higher than the other parameter values. Although the theoretical weight was high for L and D, due to the low parameter scores in most of the study area, the ratio of the score of the GALDIT index decreased, resulting in a low ratio of effective weight. The highest values of the effective index for L and D were 59.82 and 59.19 %, respectively, whereas their average values were significantly lower, at 10.53 and 14.88 %, respectively.