ريزپهنه بندي خطر سيلاب در محدوده شهرسبزوار در راستاي توسعه پايدار شهري

Microzonation of flood risk in Sabzevar suburb with the aim of sustainable urban development

به منظور پيش بيني دامنه خسارات ناشي از سيلاب جهت كنترل و مهار آن پهنه بندي خطر سيل امري ضروري است .كه هدف از اين تحقيق بررسي ميزان خطر پذيري سيلاب و ارزيابي خسارت وارده به شهر سبزوار است . پارامترهاي خاص موضوع اين تحقيق شامل ؛كاربري اراضي، تراكم جمعيت، مسيل ها، طبقات شيب، تراكم مسكوني، ضريب CN، ضريب رواناب، تراكم جمعيت، فضاي باز و قدمت ابنيه بوده سپس با تهيه لايه هاي مورد نياز محدوده شهر ، اقدام به تعيين وزن هر لايه بر اساس ميزان اهميت آن در بروز سيلاب گرديد. پس از وزن دهي نهايي، لايه ها به صورت دو به دو(AHP) توسط نرم افزار Expert choice مقايسه و ماتريس حاصل از اين مقايسات به نرم افزار Idrisi منتقل و ضريب نهايي براي هر لايه تعيين شد. در نهايت با اعمال اين ضرايب از طريق منويRaster calculator در نرم افزار ArcGis نقشه ي پهنه بندي خطر سيلاب در محدوده ي شهر سبزوار تهيه گرديد.بدين ترتيب، محدوده هاي بحراني بافت شهري در برابر سيلاب و آب گرفتگي مشخص و خسارات ناشي از سيل در قالب نقشه ي ارزيابي خسارت ارايه شد. نقشه پهنه بندي خطر سيل نشان مي دهد كه حدود 15درصد از محدوده نقشه در پهنه ي خطرخيلي زياد، 45 درصد در پهنه ي خطر زياد، 25 درصد در پهنه ي خطر متوسط و15درصد در پهنه ي كم خطر از لحاظ سيل گيري قرار دارد. هم چنين با تهيه نقشه ي ارزيابي خسارت مشخص شد كه پهنه هاي مشخص شده 80 درصد منطبق با پهنه هاي مختلف از نظر شدت سيل گيري مي باشد.

Flood risk zonation is necessary to controll and predict of the amplitude of flood damage. The purpose of this research is to evaluate the rate of flood risk vulnerability and the flood damage assessment in Sabzevar. Specific parameters of this study are land use, population density, river beds, slope classes, residential density, CN coefficient, runoff coefficient, open spaces and old buildings. After determining the necessary layers, the weight of each layer was obtained based on the importance of layer in flood occurrence. After weight determination, layers were compared with each other in a two by two basis by means of Expert- Choice software and then the resulted matrix of these comparisons were analyzed by Idrisi Software and final coefficients for layers were calculated. Finally, by applying these coefficients through Raster Calculation menu to ArcGis software, the map of flood risk zonation of Sabzevar suburb was prepared. The critical zones valnerable to flood and inundation were determined. Moreover? the possible flood loss was estimated by developin the flood damage map. Thus, flood critical zones of urban texture and inundation were prepared and then the flood loss was determined by producing the map of flood damage evaluation. The flood risk zonation map reveals that about 15 percent of study area is located in the class of very high flood risk, 45 percent is located in high flood risk class, 25 percent is located in medium flood risk class and 15 percent is in low flood risk class. Moreover? there was a compatibility of 80 percent between the classes of flood damage evaluation map and these of flood risk map.