بررسي پتانسيل سيل‌خيزي حوضه نمرود و تاثير آن بر ويژگي‌هاي اقتصادي – اجتماعي منطقه و ارايه راهكارهايي جهت مديريت آن

Assessment economic and social damage and management practices of flood (Case Study: Nimrood Basin)

امروزه سيل يكي از رايج ترين و پرهزينه ترين بلاياي طبيعي جهان است. براي پيشگيري و كاهش اثرات سيل اجتناب از قرار گرفتن در معرض اين مخاطرات و توانايي كنترل و مهار سطح آب و عمليات مربوط به آن از اهميت زيادي برخوردار مي باشند. منطقه موردمطالعه در اين پژوهش حوضه آبخيز نمرود به وسعت 7/812 كيلومترمربع مي باشد. هدف اصلي اين پژوهش تعيين پهنه هاي سيل خيز و سيل گير، حوضه رودخانه با استفاده از منطق فازي است. جهت اجراي مدل در منطقه از داده هاي مختلفي همچون بارش، كاربري زمين، خصوصيات مورفولوژيك دامنه ها مثل تحدب و تعقر(profile curvature) همگرايي و واگرايي دامنه ها (plan curvature)، شيب دامنه ها، شاخص پوشش گياهي(NDVI)، فاصله از رودخانه هاي اصلي و تراكم شبكه زهكشي استفاده‌شده است. از بين پارامترها 9 پارامتر در پهنه بندي سيل‌خيزي و 5 پارامتر در پهنه بندي سيل گيري حوضه بكار رفته اند. با آماده سازي لايه ها و اجراي توابع عضويت هر يك از آن‌ها، با استفاده از عملگر گاما عمل روي هم گذاري لايه ها صورت گرفت و نقشه پهنه بندي پتانسيل سيل‌خيزي و سيل گيري در 5 كلاس پتانسيل بدست آمد. با توجه به نقشه پهنه بندي سيل خيزي، پهنه هاي با خطر بسيار زياد در نيمه شمالي و غربي حوضه واقع گرديده اند، اغلب اين مناطق از لحاظ تراكم پوشش گياهي در سطح پاييني قرار داشته و از لحاظ كاربري زمين از نوع مرتع متوسط و فقير و نيز زمين هاي با كاربري كشاورزي، تراكم شبكه زهكشي بالا به‌ويژه در بخش هاي غربي، دامنه هاي واگرا با پروفيل محدب و مناطقي با بارش زياد را تشكيل مي دهند. در نقشه پهنه بندي پتانسيل سيل گيري، بيشتر مناطق شرقي و جنوب شرقي حوضه را مناطقي با پتانسيل سيل گيري زياد و خيلي زياد در برگرفته اند كه درمجموع 4/24 درصد از حوضه را شامل مي شود. بررسي الگوي كلي مناطق سيل گير نشان مي‌دهد كه لايه فاصله از رودخانه و ارتفاع بيشترين تاثير را براي سيل گيري دارند. اين مناطق اغلب نواحي كم شيب، سطوح همگرا با پروفيل مقعر، نواحي پست و حاشيه رودخانه ها را تشكيل مي دهند.

Introduction Zoning flood including flood reduce the risks techniques that provide valuable information about the nature and its effects flood on the floodplain lands and determining vicinity of the riverEach part of the basin has a certain potential for runoff and flooding,also different parts of the basin due to topographical features of Landforms show different potential in the flooding. Zonation of flooding and flood risk that by taking these characteristics and also production rate runoff per unit zoning does basin according to flooding and flood risk. Nowadays management method for reducing flood disasters,identification of research related to disaster reduction will require flood-related research Process of Flood disaster from 1930 to 2000 between structural flood control To reduce non-structural developments finally, combining it Continued. Several works on flood prevention and flood zonation has been made including the following Noted. Methods of data analysis Study area Nimrod is one of the areaʹs watershed Hablehrud North is located in the North East of Tehran in the Alborz Mountains of southern latitudes 52? 16´ 10 ? and 52? 44´ 24 ? East and latitudes 35? 39´ 6 ? and 35? 57´ 11 ? North. The area of this range is 812/7 square kilometers and is one of the catchment areas of Hablehrud. In terms of relative position the highest point of elevation Nimrod to a height of 4057 meters is located above sea level in the south-west in the mountains SefidAb, and the lowest point at a height of 1720 meters is located above sea level in the south-east . Figure 1 Shows Location of the study area in Tehran Province. Research Methods The main objective of this study was to determine areas of potential flooding and flood risk of basins using fuzzy logic. To implement the model in the region from different data such as precipitation, land use, the morphological properties such as convexity and concavity (profile curvature) convergence and divergence domains (plan curvature), steep slopes, vegetation cover index (NDVI), distance from major rivers and drainage density is used. Of the between parameters, 9 parameters in flood zoning and 5 parameter in flood risk zoning have used. Results and discussion With preparation of layer and implementation of the membership functions of each of them, by using gamma function, layers were placed on each other and zoning map of flooding and flood risk potential achived in fifth grade. According to flooding zoning map, Approximately 12.1% of the area have very high potential and 27.5 percent from areas are with high potential for flooding that very high risk zones have been located in the northern half and western areas. Most of these areas are low in terms of vegetation density and in terms of land use are in range of average and poor, and also included agriculture land, drainage density is high, particularly in western, divergent slopes with convex profiles and areas with high rainfall. In zoning map of potential flooding, most eastern and south-eastern areas are areas with high and very high potential, in general included 24.4% of the area. The general evaluate the pattern flood areas shows that layer away from the river and height have the greatest impact on flooding. These areas are often low-slope areas, converging levels with concave profile, low height, and neighboring rivers. Overall result So far, many methodsincluding methods scs, Boolean logic, overlap and for flood zoning is used, but the results show the capability and efficiency of the fuzzy model in Zoning flood is higher. Because fuzzy model is Logic of data transmission from given space To indefinite,other features of this model is the ability to run it in Arc GIS. According to the history of flood events in the region, show a need for comprehensive and detailed maps that can be prone areas for flooding and flood risk. Therefore In this study, according to the capabilities provided for the fuzzy logic in flood zoning, we tried use this model zonation of flooding and flood risk for Nimrod river basin. Finally, result in two zonation of flooding and flood risk were presented and each of the maps Sensitivity were classified into five classes. Situation of area in various sectors in terms of sensitivity of flooding and flood risk describe and factors affecting in each explained.