اولویت‌بندی پتانسیل سیل‌خیزی در حوضه‌های آبخیز فاقد آمار با کاربرد روش Ahp-Vikor (مطالعه موردی: حوضه آبخیز حاجی‌بختیار، استان ایلام)

هدف از این پژوهش، اولویت‌بندی پتانسیل سیل‌خیزی زیرحوضه‌ها به روش تصمیم‌گیری چند شاخصه ی ahpvikor در حوضه آبخیز حاجی بختیار در استان ایلام است که با وجود بروز سیل‌های مکرر، فاقد هرگونه ایستگاه هواشناسی و هیدرومتری است. در این مطالعه ابتدا با استفاده از تکنیک دلفی و نظرات خبرگان، شاخص‌های موثر بر پتانسیل سیل‌خیزی استخراج، سپس به روش مقایسه ی زوجی فرآیند تحلیل سلسله مراتبی (ahp)، وزن‌دهی و اولویت‌بندی شد. نتایج حاصل از اوزان نهایی شاخص‌ها نشان داد که شاخص مساحت با وزن 0.440، بیشترین تاثیر و شاخص شیب متوسط با وزن 0.096، کمترین تاثیر را در سیل‌خیزی دارد. در مرحله ی بعد به منظور اولویت‌بندی زیرحوضه‌ها به روش ویکور، حوضه آبخیز حاجی بختیار به 19 زیرحوضه تقسیم شد که 4 زیرحوضه به دلیل مستقل نبودن در این روش لحاظ نشد. سپس بر اساس شاخص ویکور، نقشه ی اولویت‌بندی زیرحوضه‌ها مبتنی بر شاخص‌های مساحت، شیب متوسط، شماره منحنی و شدت بارش در دو دوره بازگشت 25 و 50 ساله تهیه شد. نتایج این اولویت‌بندی نشان داد که در هر دو دوره ی بازگشت، زیر حوضه ی h122 با داشتن بزرگ ترین شاخص ویکور (0.994)، سیل‌خیزترین زیرحوضه و زیرحوضه ی h9 با داشتن کوچک‌ترین شاخص ویکور (0.032)، مطلوب‌ترین زیرحوضه بود و کمترین میزان سیل‌خیزی را داشت. در نهایت، زیرحوضه‌ها بر اساس شاخص ویکور در 4 طبقه ی سیل خیزی و در دو دوره بازگشت دسته بندی شد؛ به طوری که 31 درصد از مساحت منطقه در پتانسیل سیل‌خیزی متوسط، 53 درصد در پتانسیل سیل‌خیزی زیاد و 16 درصد در پتانسیل سیل‌خیزی خیلی زیاد واقع شده است. بنابراین، نتایج حاکی از حضور طبقات مختلف پتانسیل سیل‌خیزی در حوضه آبخیز مورد مطالعه است که به اقدامات مختلف سازه‌ای، بیولوژیکی و مدیریتی در این حوضه نیازمند می‌باشد.

Prioritizing flood producing potential in ungauged watersheds using the AHP-VIKOR method (Case study: Haji-Bakhtiar Watershed, Ilam)

Extended abstract1 IntroductionFlood is one of the most complex and destructive natural phenomena that cause significant damage to agriculture, fisheries, housing, and infrastructure and significantly affects social and economic activities (Chang et al., 2008). The relationship between geomorphological and hydrological parameters makes it possible to predict floods in gauged basins and generalize predictions to similar ungauged basins by creating relationships between the geomorphologically similar basins (Jain Sinha, 2003). Prioritization of areas for flood control projects is a fundamental decision that must be confirmed by studying the areachr('39')s physical, social, and economic conditions and determining the effectiveness of the plans (Djrodjetive Bruck, 1989). Subbasins with critical conditions or are close to main rivers, or public facilities (reservoir dams, diversion dams, etc.) prioritize carrying out rehabilitation projects.The region being mountainous, lack of proper past and present management of pastures, very steep slopes and slope instability, relatively severe soil erosion, the existence of rock outcrops with inadequate vegetation, and human interventions are the factors that cause flood problems in the HajiBakhtiar watershed. In the current study, the subbasins in the Haji Bakhtiar watershed will be prioritized based on the factors mentioned above. To this end, two techniques are combined: AHP and VIKOR. 2 MethodologyIn order to meet the purpose of the research, the following steps are carried out. Studying the theoretical foundations by searching library documents and using expert opinions to identify the most important indicators of flood potential in subbasins Collecting and preparing the required climate data and digital layers Calculating the weights of the indicators by using Analytic Hierarchy Process (AHP) Prioritizing (15) subbasins in terms of flood potential using the VIKOR method and preparing a subbasin potential prioritization map in two cases of 25 and 50 year return period rainfall Classifying flood potential of subbasins in 4 classes (very high, high, medium, low) based on the VIKOR method. 3 Results In the AHP method, important floodproducing indices were determined using the Delphi technique (consulting with experts) and 15 questionnaires. The results showed that the indicators affecting flood potential have different weights, based on expertschr('39') judgments, and the compatibility ratio in all questionnaires is less than 0.1. Among the indicators, the area index (final weight 0.44) has the most significant effect on flood potential, and the average slope index (final weight 0.096) has the least effect on flood potential.The range of changes in the VIKOR index of options, based on the AHPVIKOR method, varies from 0.032 to 0.994. The results of prioritizing flooding potential of subbasins, based on two rainfall intensities with 25 and 50 return periods, showed that in both cases, subbasin H122 (Palkaneh village) with VIKOR index of 0.994 has the highest priority (Maximum flooding potential) and H9 subbasin with VIKOR index of 0.032 has the lowest priority (minimum flooding potential).After prioritization in Arc GIS 10.3 environment based on the VIKOR index in two cases of rainfall intensity, the flooding potential of the subbasins were classified into four classes. The subbasin flooding potential map results at both return periods showed that, for both rainfall intensities, about 31% of the area had medium flood potential, 53% high flood potential, and 16% of the area had very high flooding potential. Out of 15 subbasins, seven subbasins are in moderate flooding condition, seven subbasins are in high flooding condition, and one subbasin is in very high flooding condition. 4 Discussion Conclusions The results obtained from the AHP method in the present study are based on aggregating the data collected by a questionnaire, which professors and watershed management experts complete. The results show that, among the four indicators affecting the flooding potential of subbasins, the area index has the most significant impact on the flooding potential of the study area. This finding is consistent with Dehghani et al. (2013) and Ozturk Batuk (2011). The rainfall intensity index is the next most important factor affecting the flood potential of the study area, which is consistent with the results of Karam and Derakhshan (2012); Dehghani et al. (2013); Yahaya (2008); and Ozturk Batuk (2011). The curve number index is the third important index, which corresponds to Khosroshahi and Saghafian (2003); Soleimani Sardo et al., (2013). Finally, the fourth index is the average slope index; this result is consistent with the results of Karam and Derakhshan (2012); Dehghani et al. (2013), and Yahaya (2008); Fernandez Lutz (2010). After calculating the weights of the indicators using the AHP method, the VIKOR method (Asghari Saraskanrood et al., 2015; Khalghi, 2002) was used to prioritize the flood potential subbasins. The flood classification potential of subbasins shows the high potential of the region in terms of flood generation. The lands with very high risk need watershed management measures such as preventing soil erosion and destruction, reducing water flow rate, increasing flood concentrationtime, creating opportunities for water infiltration in the subsoil and recharge the aquifers, and cultivating suitable plants for the conditions. The geography of the slopes and rangelands restoration should be done to change what makes the region vulnerable to its strengths.