بررسي خطر سيل‎خيزي در زيرحوضه هاي استان آذربايجان‎غربي

The Study of Flood Risk in Western Azerbaijan Province Sub-basins Using GIS

سيل از پديده هاي مخرّب طبيعي است. به‎طوركلّي، سيل‎خيزي، وضعيّت سيلاب در آن حوضه را مشخّص مي كند. عوامل بسياري در بروز سيلاب‎هاي كشور نقش دارند كه از آن ميان مي‎توان به رخداد بارش‎هاي شديد، ذوبّ ناگهاني برف در منطقه‎ي كوهستاني و عملكرد هم‎زمان هر دو عامل اشاره كرد. منطقه‎ي يك حوضه‎ي آبريز، به‎سبب وجود شرايط طبيعي مختلف، از پتانسيل رخداد متفاوتي برخوردار است. طبقه‎بندي و اولويت‎بندي زيرحوضه‎ها، گام اول را براي مقابله يا كاهش اثرهاي سيلاب در حوضه‎هاي آبريز برعهده دارد. بر همين اساس، هدف از مطالعه‎ي پيش رو، تبيين وضعيّت سيلاب در زيرحوضه‌ هاي استان آذربايجان غربي است. در همين راستا، خسارات و خطرات سيل بر اساس آمار و اطلاعات ثبت شده در گذشته تحليل شده است. براي استخراج دقيق محدوده‎ي سيل‎خيزي با استفاده از روش استراهلر به طبقه بندي رودخانه هاي استان پرداخته شد. سپس با استفاده از اين طبقه بندي براي هر يك طبقه‎ها، يك پهنه به‎عنوان محدوده‎ي خطر سيل در محيط GIS تعيين شد، در ادامه با استفاده از نقشه هاي 100000/1 زمين شناسي، واحد تشكيلات كواترنري( Qal) به اين محدوده افزوده شد. در گام بعد براي اينكه شدّت خطر سيل‎پذيري در زيرحوضه‎هاي استان مشخّص شود، از آمار وقوع سيل در زيرحوضه‎هاي استان استفاده شد و درنهايت، شدّت خطرپذيري سيل در زيرحوضه‎هاي استان به‎دست آمد. نتايج به‎دست آمده نشان مي‎دهد كه زيرحوضه‎ي زنگمار در خطر سيل‎پذيري شديد قرار دارد و لازم است تا تدابيري براي كاهش آثار سيل در اين منطقه انجام گيرد.

Introduction Flood is one of complex and destroyed phenomenon. Generally flood risk determines flood situations in each basin. Iran country have a arid climate that rainfall with high density is the main climatic features and caused many floods with destruction human, buildings and engineers structures. The object of this study is the analysis of flood situations in sub-basins of westerns Azerbaijan province. To do this statistics of flood hazards and destruction analyzed. Methodology Westerns Azerbaijan province located in the north west of Iran and have a temperate climate with rainy season in winter and autumn. Data used in this study are lithology, slope gradient, thickness of materials, humidity coefficient and rainfall rate, temperature, land use. Other data were used is Satellite data including ETM images of 2005 studied and using color composite images of 7, 4 and 1 bands recognized. Then in order to flood susceptibility areas take places with high accuracy, Straher method for river classification were used. Using this classification for each of these classes, one area titled hazard flood area calculated in GIS environment and finally Qal geology formation added this area from geology map scaled 1:100000. In next step in order to calculation of flood intensity used historical flood records. Results and Discussion The result indicated that Zangbar sub-basins have high flood hazards and need required works to mitigate floods impacts. The prepared map show Simineh Rud and Zarineh Rud subbasins have high intensity and Simineh rod have high flood areas. In generally the analysis shows 3033 residential centre and 36 urban areas located in studied province that 603 residential and 10 urban areas were located in flooded zones. The western subbasins with 125 residential centers have highest number of located in flooded areas. Conclusion Consider to location of western n Azerbaijan and due to high latitude and high elevation have high rate of snow. In addition spring season rainfall increase and caused flood occurrence. In totally all subbasins have flood susceptibility areas with low and high intensity. Then in order to combat with flood hazards in these areas is vital and different methods can be used.