نوع مقاله : مقاله پژوهشی

نویسندگان

• فرزانه ساسان پور ¹
• فاطمه محبی ²
• امیرحسین کاظم ³

¹ دانشیار گروه برنامه ریزی شهری دانشکده علوم جغرافیایی دانشگاه خوارزمی

² دانشجوی کارشناسی ارشد جغرافیا و برنامه ریزی شهری، دانشگاه خوارزمی، تهران

³ کارشناس ارشد RS&GIS دانشگاه آزاد واحد علوم و تحقیقات تهران

چکیده

سیل یکی از مخاطرات طبیعی است که هر ساله خسارات مالی و جانی فراوانی را به‌دنبال دارد. نقشه‌های پهنه‌بندی سیلاب،حاوی اطلاعات پایه و مهم در مطالعات طرح‌های عمرانی  دنیا می‌باشند و قبل از هر‌گونه سرمایه‌گذاری و یا اجرای طرح‌های توسعه، بررسی آن در دستور کار سازمان‌های ذی‌ربط قرار دارد. رودخانه طالقان طی سالیان متمادی با بروز سیلاب‌های متعددی مواجه بوده است.  اما تاکنون مطالعات جامعی در این ارتباط صورت نگرفته است. با توجه به اینکه  بـدون توجه به مخاطره سیل، سکونتگاه‌های چندی در حاشیه شاخه‌های فرعی و اصلی رودخانه احداث گردیده و حتی شـهرک طالقـان اصـلی‌تـرین استقرارگاه جمعیتی در منطقه در حاشیه آن قرار دارد، همچنین ساخت و ساز بناهـای مسـکونی و تجاری در حاشـیه رودخانـه رو به گسترش است پـژوهش حاضر به‌دنبال این است تا  بـا هـدف تعیـین پهنـه‌هـای با خطر سیل‌گیری در محدوده حوضه آبخیز طالقان به تعیین مناطقی که بیشترین آسیب از خطر سیل دارند،  پرداخته و با اسـتفاده از نـرم‌افـزار ARC GIS این اراضی را به‌صورت نقشه پهنه‌بندی مشخص نماید. تهیه نقشه پهنه‌بندی خطر سیل با استفاده از روش FuzzyVIKOR و با تعیین وزن از طریق critic برای 7 معیار مؤثر در ارزیابی پهنه‌های سیل‌گیر شامل: ارتفاع از سطح دریا، شیب، جهات شیب، کاربری اراضی، زمین‌شناسی، فاصله از آبراهه و میانگین بارش، انجام شد. نتایج این پژوهش که در پنج طبقه تهیه گردیده است، نشان می‌دهد 83 درصد از کل مساحت حوضه شامل پهنه‌های بی‌خطر یا با خطر کم می‌باشد. اما 17 درصد از اراضی آن، دارای خطر سیل‌گیری متوسط و بالا هستند که شامل عرصه‌های اطراف آبراهه اصلی و آبراهه‌های فرعی با کاربری‌های مسکونی و کشاورزی در حوضه می‌باشند. بنابراین لزوم رعایت حریم رودخانه طالقان در اراضی پست با شیب کم و متوسط، در توسعه کاربری‌های شهری روستایی منطقه، به منظور کاهش آسیب‌های ناشی از سیل، باید اجرایی گردد.

کلیدواژه‌ها

• حوضه آبخیز طالقان
• سیل گیری
• FUZZY VIKOR
• CRITIC

20.1001.1.25883860.1400.30.119.9.0

عنوان مقاله [English]

Flood risk analysis and zoning - Case study: Taleghan Watershed

نویسندگان [English]

• Farzaneh Sasanpour ¹
• Fateme Mohebbi ²
• َAmir hosein Kazem ³

¹ Associate Professor of Kharazmi University

² Graduate student of Geography and Urban Planning at Kharazmi University

³ Master of RS & GIS Azad University, Science and Research Branch, Tehran

چکیده [English]

Extended Abstract
Introduction
Floods are natural hazards that cause a lot of financial and human losses every year. Flood zoning plans contain basic and important information in the study of development projects in the world, sobefore any investment or implementation of development plans, they should be reviewed by the relevant organizations. The Taleghan River has faced numerous floods over the years,however, no comprehensive studies have been conducted regarding the damage caused by the flood of Taleghan River and its zoning. Taleghan town, which is the main population settlement in the region, the river passes through and the construction of residential and commercial buildings along the river, is expanding. By Using the ARC GIS software,Taleghan most affected areas by flood risk have been determined in the form of a zoning map. Flood risk zoning map has been preparedby using FuzzyVIKOR method, determining the weight through the critic for 7 effective criteria in evaluating flood zones including: altitude, slope, slope directions, land use, geology, distance from waterway and average rainfall. The results of this study, which has been prepared in five categories, show that 83% of the total area of the basin includes safe or low-risk areas. However, 17% of its lands have moderate and high flood risk, which includes areas around the main waterway and sub-waterways with residential and agricultural uses in the basin. Therefore, in order to reduce floods,in low and medium slope lowlands of Taleghan River, in development of rural urban uses in the region, it should be implemented.
 
Materials and Methods
The present research is descriptive-analytical in terms of method and applied research in terms of purpose. Many factors must be considered in flood zoning, with different degree of importance. In this study, based on previous experiences, the factors that had the greatest impact on flood occurrence in the Taleghan watershed were selected in the VIKOR Fuuzy model. The data used in this study include sea level elevation, slope, slope directions, average rainfall, distance from waterway lines, land use and formation, which were used to determine areas vulnerable to floods.Some part of the required data including Digital Elevation Model (DEM), land use map of the region and map of geological formations have been collected in raw form with a shape file format in the scale of 1: 250,000 from the rangeland and watershed management department of the Faculty of Agriculture and Natural Resources, University of Tehran. Elevation, slope and geographical aspect, maps were extracted from DEM 10 m. The layer of waterways, including permanent canals and rivers, was provided by the National Forests, Rangelands and Watershed Management Organization. The map contains same rain line that is received from the Meteorological Organization. The raster map of the average precipitation of the basin that was prepared based on the information of the precipitation rain lines and the statistics of rainfall data related to 5 stations of Dizan, Ciancranchal, Gotehdeh, Jostan, Glird, Armut and Zidasht, using the Interpolation technique. The criteria were normalized after preparing the maps (GIS READY) and applying the required edits such as defining the unit coordinate system for the maps, eliminating the errors that occurred during digitization and reducing the descriptive data by adding a new column to the related descriptive information table.
In all of the maps thatwere converted from Vector format to Raster, after the normalization step, the layers were weighed through the Critic method. Using the VIKOR model and the weights obtained by the Critic method, which were calculated in Excel software, the value of the VIKOR index (Q) was obtained for every option (pixel). Finally, the ultimate map of flood risk zoning in Taleghan watershed resulted from assigning the values of VIKOR index (Q) obtained from the previous step for every relevant point (option), by ARC GIS software.
 
Results and discussion
The results of flood zoning map show that 83% of the total area of the basin includes safe or low risk areas. However, 17% of this area has a moderate and high flood risk, which mostly includes urban, rural settlements, orchards and agricultural lands, which shows the importance of paying attention to proper management in these areas. According to the results, it can be said thatthe distance from the waterway in Taleghan watershed has had a significant effect on the amount of flooding, so by moving away from the main waterway and sub-waterways of the basin, the risk of floods and flooding can be reduced. The results of the terming flood risk zoning, show that 27 villages and settlements out of 68 villages in the region are in high-risk areas, including the villages of Eskan, Gotehdeh, Narian, Prachan, Mehran, Joostan, Nisa Olga, Hasanjoon, Jazan, and Mochan are at the highest risk.
 
Conclusion
It has been proved that Multi-criteria decision analysis methods in GIS is a robust approach to generating risk maps with acceptable accuracy. The judgment about the acceptabilityof the model can be made byusing external information from real ground data. In this study, relatively high compliance with the final zoning map was obtained by checking the history of floods in the study area.

کلیدواژه‌ها [English]

• Taleghan watershed
• Flooding
• VIKOR Fuzzy
• GIS