ارزيابي مدل منطق فازي در مقايسه با ساير مدل هاي مفهومي در پهنه‌بندي سيل‌خيزي با تاكيد بر ويژگي هاي ژيومورفولوژيك، مورد شناسي: حوضه داورزن

Evaluation of Fuzzy Logic Relative to other Conceptual Models in Zoning of Flooding with Emphasis on Geomorphological Aspects Case study: Davarzan Basin

سيل مخاطره اي طبيعي و رويدادي ناگهاني، سريع و مخرب است. مطالعات گذشته گوياي آن است كه علاوه بر ويژگي هاي بارش، خصوصيات مورفومتريك و ژيومورفوژيك حوضه هاي آبخيز در كميّت و كيفيّت اين پديده نقش اساسي دارند. حوضه ي آبخيز داورزن در غرب دشت سبزوار واقع شده است. همه ساله سيلاب هاي مخربي در اين حوضه به وقوع مي پيوندد. هدف از اين پژوهش، بررسي علل و عوامل موثر در وقوع سيل از جمله، شيب، ليتولوژي، اشكال ناهمواري (تيپ‌هاي فيزيوگرافي) ، نوع خاك، CN و وضعيت و گرايش پوشش گياهي و سپس تجزيه و تحليل سيل خيزي اين حوضه است. براي دست يابي به اين هدف از روش تلفيق عوامل موثر با استفاده از تكنيك پهنه‌بندي در مدل هاي مفهومي و قابل اجرا در محيط GIS از جمله مدل منطق بولين، مدل شاخص همپوشاني و مدل منطق فازي در قالب لايه‌هاي اطلاعاتي استفاده شده است. روش تجزيه و تحليل بر پايه يك مقايسه تحليلي و دست يابي به نتايج حاصل از اين مدل-ها استوار است. به كارگيري اين مدل ها در محيط سيستم اطلاعات جغرافيايي از طريق وزن دهي به متغيّرهاي موثر بر سيل ‌خيزي حوضه بر اساس شدت و ضعف تاثيرگذاري آنها توانسته است شكل‌گيري سيل را در حوضه و در قالب پهنه هاي مشخص ارزيابي نمايد. همچنين نتايج حاصل از مقايسه ي مدل هاي به كار گرفته شده نشان مي دهد كه مدل فازي گاما شاخص ترين ابزار مفهومي براي تعيين پهنه هاي در معرض سيل خيزي در اين منطقه مي باشد.

The nature has always shown its destructive face with the phenomena such as floods, volcanoes, earthquakes and ....These risks have been always considered as a threat to human activities. Davarzan basin as a case study has been studied from this approach. This basin is located in west of Sabzevar Plain. The area of this basin is equal to 498.69 kilometers. The issue under study is that every year a large portion of the river water is wasted and damages to agricultural activities. The research aim is to determine the flooding zones by zoning maps. Lack of hydrometric station, hydrological data and statistics and impassable of the areas at upstream of the basin for field works and the necessity for long term measurements have been the main problems of this research . In this study, GIS software and conceptual models have been used as the main tools. In determining the flooding zones, several factors are involved and each with different degrees of importance impact on zoning, thus, the natural condition like slope, lithology, morphometry, soil type, CN and vegetation condition are the main data of research. However, fuzzy algebraic sum operator as recognized 91.03% of the basin with very high flooding and 0 .13 percent with flooding and therefore davarzan basin has low flooding sensitivity.Thus the fuzzy gamma operator among all operators in the models studied in GIS, has the high accuracy in flood zoning of basins in davarzan basin. This model also has determined 18.82 percent of the basin located in high zone of flooding and 24.62 percent of basin is placed in very high flooding. Units that are consistent with low flooding shall have the lowest weight. So that 19.32 percent has been identified as low flood and 37.24 percent as moderate flood. Finallt, the final result has been presented in the form of zoning maps.