triangular fuzzy number

Desertification is a complex socio-economic issue resulting from the interaction of several factors. This phenomenon is always in uncertain environments and is strongly influenced by vague and implicit judgments. Therefore, the use of multi-criteria fuzzy decision-making mechanisms seems necessary in evaluating desertification strategies. On the other hand, often the input data to these devices are inaccurate and variable. So, performing sensitivity analysis on output data is an important step in such evaluations. The aim of this study was to analyze the sensitivity of priority strategies in the Yazd-Khezrabad sub-catchment in central Iran.

In order to achieve this goal, first in the framework of fuzzy multi-criteria decision-making method and with using triangular number, fuzzy pairwise comparison decision matrix was formed and the initial priority of strategies was estimated. Then the sensitivity analysis process was performed separately on the criteria and strategies in the framework of the Triantaphyllou-sensitivity analysis model. Following the determination of the most sensitive criteria and strategy, new weights of criteria and strategies were replaced based on the most sensitive criteria and strategy in the decision matrix. By calculating the weighted average of each row of the modified normalized matrix, the degree of preference or final weight of the strategies was estimated.

The results showed that the adjustment strategy in groundwater abstraction (A31) is still considered as the most important strategy as the initial results with a degree of preference of 92.9%. While the ranking of other strategies has undergone serious changes.

It is concluded that according to the mentioned macro strategy, the process of desertification can be slowed down and the destroyed areas revived by implementing aquifer projects, improving irrigation methods, land improvement, controlling the growth of industries and aquaculture crops.

Desertification is a natural disaster risk event. This phenomenon, along with the extent of degradation, various effects and complexity of the process, deals with qualitative and uncertain indicators and follows the behavior of fuzzy systems. Therefore, in evaluating combating desertification to achieve preferred and optimal strategies, the use of multi-criteria fuzzy decision-making methods seems necessary. Therefore, this study was conducted to determine the priority of strategies to combat desertification using hierarchical analytical models in a fuzzy environment in the Yazd-Khezrabad plain during 2019-2020 as a case study.

Fuzzy decision matrix was obtained from fuzzy Delphi method and within the framework of multi-criteria decision-making method. Using Expert Choice software and ELECTRE model, the initial priority of strategies was obtained. In order to estimate the final priority of strategies, TOPSIS method was used and the results were analyzed using GAIA diagram, Graphical Analysis for Interactive Assistance, in Visual PROMETHEE software environment.

The results show that the strategy of "adjustment in abstraction from groundwater resources" (A31) with a ratio of 56.59% is the most important strategy in controlling and reducing the effects of desertification and rehabilitation of degraded lands. The strategies of livestock grazing control (A20), irrigation pattern change and implementation of low water requirements (A33), vegetation development and restoration (A23) and prevention of improper conversion and change of land use (A18) with proximity ratios of 15.76 %, 13.53%, 11.34% and 2.78% were selected as the next priorities, respectively. Analyses performed in Visual PROMETHEE software environment also confirmed the results of the ranking. As the analysis showed, the strategy of "adjustment in abstraction of groundwater resources" (A31) with a pure out ranking progress of Phi = 0.3635 still remained the most preferred evaluation strategy and other strategies were ranked as before.

Overall, it is concluded that in line with the strategy of adjusting the abstraction of groundwater resources (A31), by implementing aquifer projects, improving irrigation methods, land improvement, controlling the growth of industries and aquaculture crops, the process of desertification can be slowed down and destroyed lands can be restored. It is suggested that in the plans to control and reduce the effects of desertification and rehabilitation of degraded lands, the obtained results and rankings should be considered.