Comparison of Delphi and Analytic Hierarchy Process (AHP) techniques in locating flood spreading

A main part of Iran is considered as arid and semi-arid regions as well as water is one of the limited factors for these areas. Controlling the destructive floods is an important activity due to destructive floods and water shortages. In this regard, flood spreading is an effective strategy to control and use floods. To determine suitable areas for flood spreading and direct water into a permeable formation is one of the most important factors in determining the success of flood spreading projects. The present study was conducted to combine and compare the Delphi and Analytic Hierarchy Process (AHP) for flood spreading in Ivar watershed, NE Iran. For this purpose, 4 main criteria, 8 subcriteria and 24 indices were selected. Percentage and degree of importance for criteria, sub-criteria and indices of flood spreading was determined by AHP in Expert Choice. Questionnaire forms were filled in by experts so that those which have high degree and percentage of importance are more important. After that, the maps were prepared by geographic information system (GIS). Based on the results of AHP and Expert Choice, the highest and lowest relative importance was recorded for sediment volume and Unemployment rate, respectively. According to Delphi technique, indices of soil permeability, flood quality, soil texture, slope, aqueduct, and sub-criteria of water, aquifer, topography, as well as criteria of permeability and flood are important in order in locating flood spreading for Ivar watershed. According to the results of the techniques used in this study, it is revealed that criteria, sub-criteria and indices in Delphi and AHP have approximate results. Hence, using these techniques interchangeably in location of flood spreading can be effective and practical. © 2016 Elixir All rights reserved. Elixir Earth Science 94 (2016) 39993-39999 Earth Science Available online at www.elixirpublishers. com (Elixir International Journal) Hamid alipor et al./ Elixir Earth Science 94 (2016) 39993-39999 39994 the process is stopped after a predefined stop criterion (e.g. number of rounds, achievement of consensus, stability of results) and the mean or median scores of the final rounds determine the results (Helmer, 1997). The Delphi Method is not to be confused with a related technique for manufacturing consent in which an organizing party combines the input in a non-transparent way, giving the organizing party complete but non-obvious control over the outcome. A name often used for this deceptive use of the Delphi Method is the "Delphi Technique" (Rowe and Wright, 1999). Delphi is based on the principle that forecasts (or decisions) from a structured group of individuals are more accurate than those from unstructured groups (Wissema, 1982). The technique can also be adapted for use in face-to-face meetings, and is then called miniDelphi or Estimate-Talk-Estimate (ETE). Delphi has been widely used for business forecasting and has certain advantages for other fields such as environmental agents. There have been conducted different studies on the application of GIS, remote sensing, and Decision Support Systems (DSS) in various fields (Ramalingam and Santhakumar, 1997; Kheirkhah Zarkesh, 2005; Ghaiomian et al., 2005). Zehtabian et al., (2001) showed fuzzy operator of gamma = 0.1 and gamma = 0.3 was the most appropriate location for Toqrood watershed in Qom province, center of Iran. GIS and remote sensing were applied to disperse flood in Zanjan province, west of Iran (Abdi, 2005). In addition, Delphi technique was used to determine the areas with high potential of flooding so that these areas were weighted and located (Majnonian, 1997; Gholami, et al. 2005). Miller and Cuff (2005) indicated that Delphi technique was determined as an appropriate technique for environmental problems. Moreover, Delphi and AHP techniques were compared to locate flooding after fire in forest (las Heras, 2007). Material and methods Ivar watershed with an area of 5500 ha was located in northern horasan ran longitude to latitude to maximum and minimum a.s. l. was respectively 1603 and 1031 m) (figure1). It is in arid class based on Dumbarton classification. The mean annual temperature is 14.1 °c, which is ranging from 8.1 oc of winter to 40.1 oc of summer. The Agriculture, livestock and carpet weaving are the major occupations of local people. The location of Ivar watershed have been presented in figure 1. The watershed is covered by sedimentary and rocks from Jurassic, Cretaceous and Quaternary. Figure 1. The location of Ivar watershed in Iran In the present study, the map (scale of 1:25000) of elevation classes was prepared from data of National Cartographic Department, and then georeference process was done. After that, DEM was applied to create elevation and slope maps of the watershed. Slope map was classified into five classes of 0-2, 2-5, 5-8, 8-12, and more than 12. The geological map of the watershed was extracted from 1:100000 map of geological department of Iran. In addition, ETM+ of 2002, 1:50000 topographic maps, and 1:45000 aerial photographs were used in this study. Surface permeability map based on hydrological groups of soil were digitized in GIS and classified in four classes as very high, high, medium, and low. In AHP technique, a decision-maker should compare every pair criteria involved in making decision, which this comparison in first step was presented as descriptive and in next step as quantitative form from 1 to 9 (Table 1) and finally a matrix would be obtained of this comparison (Satty, 1980). Table 1. Determining the criteria value in respect to each other by expertise in AHP. Value Preference 9 Totally Preference or very important 7 Very strong Preference or importance 5 Strong Preference or importance 3 Weak Preference or importance 1 Same Preference or importance 2, 4, 6, 8 Preferences between above intervals All main criteria had some sub-criteria, which were assessed by experts. After extracting all sub criteria and criteria in this study, the incompatibility rate was obtained by expert’s views. Controlling the incompatibility rate of decision-maker was performed based on mathematical relations and Expert Choice software. The incompatibility rate was obtained for determining the accuracy of pair-comparison matrixes in Expert Choice. The sample of this incompatibility rate has been presented in figure 2. If the incompatibility rate is less than 0.1, it can be concluded that there is an appropriate value of compatibility in pair-comparison; otherwise this indicates incompatibility (Ataie, 2010; Ghodsipour, 2009; Ishizaka & Labib, 2009; Malczewski, 2006; Saaty, 2002; Oswald, 2004) (figure 3 Making-decision tree of criteria, subcriteria and indices for spreading flood based on AHP). Figure 2. The sample of the incompatibility rate using Expert Choice. Hamid alipor et al./ Elixir Earth Science 94 (2016) 39993-39999 39995 Figure 3. Making-decision tree of criteria, sub-criteria and indices for spreading flood based on AHP The importance of criteria and sub-criteria regarding their practical aspects has been created in a new form. For this purpose, the questionnaire forms including the criteria were designed and filled by experts (table 2). After that the scores were collected and the criteria weighted. Table 2. The degree of importance for criteria in respect to each other by expertise in Delphi technique. The results of the Delphi questionnaire were applied to calculate two numerical indices of the degree and percentage of importance. Then these two indices were graphically obtained for selecting flooding criteria. Mathematical relationships of percentage and importance are as follows (Danehkar and Hadadinia, 2009):