پديد آورندگان :
روحاني، حامد نويسنده استاديار گروه مرتع و آبخيزداري، دانشگاه گنبدكاووس , , محمدي استادكلايه، امين نويسنده - ,
كليدواژه :
آنتروپي , ويكور , حوضه آبخيز قورچاي , پتانسيل سيل‌خيزي
چكيده فارسي :
جامعه انساني و گستره طبيعي به‌طور فزاينده‌اي به مناطق آسيب‌پذير در مقابل بلاياي طبيعي مانند سيل تبديل‌شده‌اند. اين وضعيت در دو دهه گذشته به‌ويژه در استان گلستان به‌خصوص حوضه آبخيز قورچاي كه يكي از مهم‌ترين مناطق سيل‌خيز استان كه در چند سال گذشته سيل‌هاي مخرب و ويرانگري به وقوع پيوسته است، تشديد شده است. با توجه به منابع محدود مالي، اولويت‌بندي مكاني اجراي پروژه‌هاي آبخيزداري در مناطق با پتانسيل سيل‌خيزي بالاتر سبب افزايش حداكثري نتايج مي‌شود. ازآنجاكه پارامترهاي متعدد كمي و كيفي بر پتانسيل سيل‌خيزي تاثيرگذار هستند و بعضاً متضاد با يكديگر، انتخاب مناطق حساس دشوار و پيچيده مي‌باشد. از طرف ديگر با توجه به عدم قطعيت در تصميم‌گيري به دليل خطاي موجود در دقت داده‌هاي پايه و نظرات متضاد كارشناسي، براي بررسي اهميت نسبي معيارها و زيرمعيارها يك فرايند دومرحله‌اي براي حل مسيله ارايه‌شده است. در الگوريتم پيشنهادي ابتدا با روش بردار ويژه و آنتروپي اهميت نسبي معيارها تعيين سپس روش بازنمونه‌گيري بوت استرپ به‌منظور به‌روزرساني ماتريس اوليه با توجه به وزن‌هاي اوليه محاسبه‌شده استفاده گرديد. سپس ماتريس تشكيل‌شده با روش ويكور بي‌وزن شده و مناطق بحراني ازنظر پتانسيل سيل‌خيزي اولويت‌بندي شد. مزيت روش ويكور نسبت به ساير روش‌هاي تصميم‌گيري چند متغيره استفاده از داده‌هاي خام در سطح زير معيارها و بدون در نظر گرفتن نظرات كارشناسي است.
چكيده لاتين :
Human society and the natural environment have become increasingly vulnerable to natural hazards like flood. In last two decades, the situation is particularly acute in Golestan province particularly in Gorchay watershed, which is one of the most floods -prone regions of the province which has long experienced large-scale floods of devastating proportions. The rural and unregulated Gorchay River watershed located in central Gorganrood basin has a highly variable flow regime and a wide range of instantaneous peak flows. Funding for watershed restoration is limited. It is important to identification of critical area for prioritize by need and implement projects that will maximize watershed management efforts. On the other hand, flood risk management is an extremely complex, multidisciplinary field with conflicting criteria that must be considered. Multiple criteria decision making is a collection of methodologies to compare, select, or rank multiple alternatives that involve incommensurate attributes. In spite of the above continuing efforts, the fundamental weakness in parametric flood hazard risk still exists when the weights on evaluation criteria are determined. On the other hand the analysis is inevitably associated with a noticeable degree of uncertainty due to the vagueness of data and caused by the subjective viewpoint of the decision maker. Therefore, this study proposes a new procedure to reduce the uncertainty of weights derivation techniques based on Entropy and Eigen vector combined by non-parametric resampling bootstrap method for assigning the weights of relative importance of attributes. In this paper we show the use of the Compromise Ranking Method, also known as the VIKOR method, in the identification of flood prone area on sub watershed prioritize.
Methodology,
The criteria were divided into four characteristic groups: Morphometry, hydroclimatology, land use and lithology components. In addition, 6, 4, 5 and 4 criteria were selected for the Morphometry, Hydroclimatology, land use and geology, respectively. For example, slope has a dominant effect on the contribution of rainfall to stream flow. It controls the duration of overland flow, infiltration and subsurface flow. Drainage is one of the important indicators of the landform element and provides a numerical measurement of landscape dissection and runoff potential. This means that the higher the density, the higher the catchment area is susceptible to erosion, resulting in sedimentation at the lower grounds. One of the sub criteria rainfall intensity with 25 yr return period which was considered and interpolated using Kriging method to create a continuous raster rainfall data within and around municipality boundary. The land-use and land-cover management of an area is also one of the primary concerns in flood prone area because this is one factor which not only reflects the current use of the land, pattern and type of its use but also the importance of its use in relation to soil stability and infiltration. Runoff of rainwater is much more likely on bare fields than those with a good crop cover. In next step, in order to apply the VIKOR method, we need to generate appropriate weights for attributes. First, the relative importance between two criteria is measured according to a numerical from 1 to 9 for each evaluation criterion according to the decision maker’s pairwise comparisons of the criteria. The higher the weight is the more important the corresponding criterion. Entropy in information theory is a criterion uses for measuring the amount of disorder represented by a discrete probability distribution. The principal eigenvector of the pairwise comparison matrix is figured out to produce a best fit to the weight set. Then non-parametric resampling bootstrap method is applied to generate weights for attributes. VIKOR method is based on an aggregating function representing “closeness to the ideal” which originates in the compromise programming method. This comprising method can be used to obtain a nearly ideal solution according to all established criteria. Combining the VIKOR method with our new suggested procedure for weighting the importance of the different criteria, allows the decision-maker to systematically assign the values of relative importance to the attributes based on their preferences.
Results and discussion,
In the application for Gorchay watershed as a result, the most important criteria were found to be lithology follow by morphometry with weight equal to 0.427 and 0.260, respectively. In the sub criteria comparison between four hydroclimatolgical and six morphometric factors considered in this study, rainfall intensity equal with time of concentration and slope steepness were concluded to be the most critical factors. Among the sub criteria of the land use, the bare soil show high weighting value. Then priority ranks of the alternatives were determined by the Vlse Kriterijumska Optimizacija I KOmpromisno Resenje (VIKOR) to rank subbasin with respect to the criteria. Based on the final result the major flood prone area of the watershed were subbasin 14 and 10 which were ranked as the 1st and 2nd major flood prone areas using the new weighting approach and bootstrap- VIKOR procedure.
Conclusion,
We are aware of a few natural hazard mitigation policies developed to assist people of floodplain area; however, policy makers need to priorities their natural hazard mitigation resources to the most vulnerable places. Hence, multi-criteria decision analysis method would be a useful approach for flood disaster planning in terms of resource allocation. The major advantage of VIKOR method over multiple criteria decision making methods is that it uses linear normalization and the normalized value does not depend on the evaluation unit of a criterion.
