Monitoring of the Actual State of Desertification using VPM and WASPAS Scoring Models

Considering the spread of desertification and the emergence of its extensive and long-term effects on the environment and human activities, appropriate management methods can reduce the intensity and spread of this phenomenon. Therefore, executive actions in this field should be based on knowledge of the current state of land desertification and its future development. Therefore, this research was conducted to evaluate the risk of desertification using VPM and WASPAS scoring models and a geographic information system as a case study in the Yazd-Khizrabad Plain from 2021 to 2022. In the framework of these models, effective indicators are identified based on field and library studies. The working units were then determined by the geomorphology method and the importance of the indicators in each unit was obtained in the form of pairwise comparisons based on the Delphi method. Next, the importance of the indices was estimated using the Shannon entropy method, and a decision matrix was formed. After balancing, zoning of the desertification intensity potential was performed by calculating the desirability coefficient using the VPM and WASPAS scoring methods in the ArcGIS software environment. results obtained showed that the land units of the Mountain Agriculture Ground (MAG) and Plain Agriculture Ground (PAG) have the highest desertification potential, which covers 7335.86 ha (35.9%) of the entire study area. Most of the land in the region is under the influence of desertification with a relatively moderate intensity (III). The quantitative value of the desertification potential for the whole region based on all the indicators was placed in the middle class (IV). The results of this study indicate the efficiency and ease of application of the VPM and WASPAS point approach techniques in evaluating the intensity of desertification.
 
Extended Abstract
1-Introduction
Considering the spread of desertification and the emergence of its extensive and long-term effects on the environment and human activities, appropriate management methods can reduce the intensity and spread of this phenomenon. Therefore, executive actions in this field should be based on knowledge of the current state of land desertification and its future development. Despite the development of quantitative techniques in recent years, considering the practical importance of desertification risk-zoning maps, there has been, an attempt to provide methods with less error and higher reliability. Therefore, this research was conducted to evaluate the risk of desertification using VPM and WASPAS scoring models and a geographic information system as a case study in the Yazd-Khizrabad Plain from 2021 to 2022.
 
2-Materials and Methods
In the framework of these models, effective indicators are identified based on field and library studies. The working units were then determined by the geomorphology method and the importance of the indicators in each unit was obtained in the form of pairwise comparisons based on the Delphi method. Next, the importance of the indices was estimated using the Shannon entropy method, and a decision matrix was formed. After balancing, zoning of the desertification intensity potential was performed by calculating the desirability coefficient using the VPM and WASPAS scoring methods in the ArcGIS software environment.
In the WPM scoring method, the value of work units for indicators reached the root of index weight by Eq. 1. Then, the power utility values ​​were estimated from the row multiplication of the components of the weighted-root matrix (Eq. 2).
                                                                                                                                       (1)                                                                                                                                 
                                                                                                                                (2)                                                                                                                        
In the WASPAS scoring method, to estimate the desirability of the components of the decision matrix, the weight of the indicators was multiplied and the weighted matrix was obtained.
                                                                                                                            (3)                                                                                                                         
Then, the values ​​of multiplicative utility were estimated from the row sum of the components of the multiplicative weighted matrix using Eq. 4.
                                                                                                                             (4)                                                                                                                        
The components of the root-weighted matrix ( were obtained by rooting the weight of the indicators of the components of the decision matrix (Eq. 5).
                                                                                                                                     (5)                                                                                                                             
After estimating the root-weighted matrix, the root utility values were estimated from the row multiplication of the components of the root-weighted matrix using Eq. 6.
                                                                                                                             (6)                                                                                                                  
Finally, the final desirability of options (U_i), or in other words, the desertification potential of work units was obtained from the average values of multiplicative desirability and root (Eq. 7).
                                                                                                                        (7)                                                                                                                
Finally, to facilitate and accurately analyze the data and achieve the results, based on the degree of desirability obtained from both models and using Arc GIS9.3 software, the erosion potential was mapped.
 
3- Results and Discussion
The correlation coefficient of the results obtained from the analyses of both models was significant at the 99% level. At the same time, the comparative study showed that the land units of the Mountain Agriculture Ground (MAG) and Plain Agriculture Ground (PAG) have the highest desertification potential, which covers 7335.86 ha (35.9%) of the entire study area. Most of the land in the region is under the influence of desertification with a relatively moderate intensity (III), which includes Sandy Dune with Plant Cover (SDPC) (SDPC), industrial lands (IA), Eppandage Plain with Plant Cover (EPPC), and Bare Plains with Plant Cover (BPPC). Also, in the study area, there is no severe (VI) and relatively severe (V) desertification class. The quantitative value of the desertification potential for the whole region based on all the indicators was placed in the middle class (IV).
According to the analysis and the results obtained, it can be concluded that the scoring approach in evaluating the intensity of desertification and preparing a zoning map is a fast and relatively accurate method in evaluating the intensity of desertification. The most important features of this approach are considering quantitative and native indicators, its simplicity and step-by-step, the geomorphology method in determining zoning units, the method of weighting indicators with group polling in the framework of the table, the same scoring, the method of weighting the indicators to each other from the Shannon entropy method and using the geographic information system. This approach can be used in future evaluations of desertification and, if necessary, it has the necessary flexibility by selecting local indicators.
 
4- Conclusion
The results of this study indicate the efficiency and ease of application of the VPM and WASPAS point approach techniques in evaluating the intensity of desertification. It is suggested that in the plans to control and reduce land erosion and destruction, by paying attention to the analyses made, this chaotic situation will be quickly improved, and a stable structure will be established in the process of dealing with erosion. As a result, while preventing the wastage of limited funds, the success rate of implementing erosion management plans will increase.