كليدواژه :
پايش بيابان‌زايي , كاربري اراضي , سنجش از دور , شرق اصفهان
چكيده فارسي :
روند روز افزون تخريب منابع طبيعي در بسياري از نقاط جهان، تهديدي جدي براي بشريت محسوب مي شود. بيابان زايي يكي از مظاهر اين تخريب مي باشد كه در حال حاضر به عنوان يك معضل گريبان گير بسياري از كشورهاي جهان از جمله كشورهاي در حال توسعه مي باشد. در حال حاضر سنجش از دور يكي از فن آوري هايي است كه با داده هاي بهنگام و دقت مناسب براي پايش تغيير كاربري اراضي در عرصه هاي منابع طبيعي مي باشد. هدف از اين تحقيق ارزيابي تغييرات كاربري اراضي به منظور پايش بيابان زايي با استفاده از تكنيك سنجش از دور در منطقه شرق اصفهان اراضي كشاورزي اطراف زاينده رود مي باشد. در اين مطالعه از تصوير سنجنده هاي tm به تاريخ 1366،1377، etm+به تاريخ 1381و oli به تاريخ 1393 مربوط به ماهواره لندست5،7 و 8 جهت بدست آوردن نقشه كاربري اراضي استفاده و بعد تصحيح هندسي و راديومتريك انجام گرفت. سپس از تركيب رنگي كاذب، آناليز مولفه اصلي، شاخص گياهي و روش طبقه بندي نظارت شده جهت بارزسازي عوارض و از الگوريتم حداكثر احتمال به عنوان مناسب ترين روش در طبقه بندي نظارت شده در 9 طبقه از پوشش اراضي استفاده گرديد. پس از توليد نقشه كاربري اراضي عمليات ارزيابي صحت با محاسبه ماتريس خطا و سپس عمليات آشكارسازي براي اين نقشه ها انجام گرفت. در نهايت جهت پايش بيابان زايي، تغييرات 27 ساله كاربري اراضي اطراف زاينده رود با استفاده از روش مقايسه به شناسايي تغييرات پرداخته و مساحت هر كاربري بدست آمد. نتايج نشان داد كه در دوره زماني 27 ساله، حاشيه رودخانه زاينده رود تغييرات چشمگيري داشته، به طوري 86.43 درصد حاشيه رودخانه به دليل گسترش فعاليت هاي كشاورزي در حريم رودخانه و خشك شدن رودخانه، تخريب شده است. از ديگرتغييرات بارز، كاهش قابل توجه اراضي كشاورزي مي باشد به طوري كه 64 درصد اين اراضي نسبت به سال 1366 كاهش يافته است. از دلايل كاهش اراضي كشاورزي مي توان به خشكسالي حاكم بر منطقه و خشك شدن رودخانه زاينده رود و همچنين كاهش نزولات جوي وتغيير كاربري اراضي و همجواري اين منطقه با كوير اشاره كرد. همچنين حدود 324.99 هكتار از اراضي شوره زار به اراضي كشاورزي تبديل شده است. علاوه بر اين، مناطق شهري هم توسعه يافته كه درتوسعه آن اراضي كشاورزي و مرتع نقش داشته اند. اراضي باير اطراف زاينده رود نيزافزايش و همچنين در منطقه از اراضي مرتعي كم و به اراضي باير وتا حدودي به كشاورزي افزوده شده كه استفاده نامناسب از اين اراضي را به منظور كشاورزي نشان مي دهد. كه اين بيانگر پيشرفت بيابان زايي در منطقه است. به طور كلي روند بيابان زايي در اين دوره 27 ساله يك روند رو به رشد داشته است. بنابراين داده هاي ماهواره اي چند زمانه و چند طيفي جهت بارزسازي خصوصا در مورد پايش بيابان زايي داراي قابليت وسيعي مي باشد و روش مقايسه پس از طبقه بندي براي مشخص شدن نوع و جهت تغييرات رخ داده مفيد است.
چكيده لاتين :
Trend of increasing natural resource degradation in many parts of the world, is a serious threat to humanity. Desertification is one of the manifestations of the damage that has already suffered as a scourge of many countries, including developing countries are. At present, remote sensing is one of technologies with timeliness data and accuracy suitable for monitoring land use changes in the areas of natural resources. Desertification monitoring and tracking changes, which seeks to desertification that the change could be for any reason and also collect and analyze data from activities, projects, plans and programs that may desertification range condition assessment and reporting to provide them. The purpose of this study was to evaluate changes in land use on desertification monitoring using remote sensing techniques to the agricultural lands around zayandeh rood in the East region of Isfahan.
materials and methods
In this study, the image sensor of TM to date 1987, 1998, ETM+ to date 2002 and OLI to date 2014 related to the Landsat 5,7 and 8 to obtain the land use map used and then was performed radiometric and geometric correction.Then was used the color combination, the main component analysis, vegetation index and supervised classification method for detection of complications and the maximum likelihood algorithm as the most appropriate method for supervised classification in classes 9 of land cover. After production the land use map correctness evaluating operations with calculation error matrix and then was performed detection operations for these maps. Finally, for desertification of monitoring, land use years 27 changes around zayandeh rood using the comparison method is paid changes to identify and was obtained the area of each use.
Results and discussion
For investigate the the process of desertification, land use changes in the period of 27 years. In order to select the appropriate bands in supplying the best color composite satellite images and operations classified in order to reconstruct the images, index optimization factor was applied. The results of accuracy assessment shows that For all the images above the 80% overall accuracy and Kappa statistics indicate that almost 80 percent. Generally good agreement between the classification and classes of users on the ground there. By comparing bit images specified land use changes in the period of 27 years, riverbank has the greatest changes during this period. So during these 27 years the river high Zayandehrood degradation, which could be due to the expansion of agricultural activities in rivers. This degradation is generally represents gradual drying of the river and go surrounding cultivated by farmers. This degradation process in the margins of the river and the gradual drying of the river towards the desertification situation in the region shows.
Conclusion
In year 27 time period, Zayandeh Rood neighboring rivers has changed dramatically, so 86.43% of neighboring rivers was destroyed due to the expansion of agricultural activities vicinity of the river and drying river. Another significant changes, loss of agricultural land is notable such that 64% of this land has been reduced compared to 1987. Of reasons for the loss of agricultural land will be noted the region drought and Zayandeh Rood river drying up and Low rainfall, land use change and the proximity of the region desert. Also, has become about hectares 324.99 Of salt marsh lands to agricultural land. Moreover, the developed urban areas to its development contributed agricultural land and rangeland. Bayer lands around Zayandeh Rood Increase and also in region of rangeland lands Low and has increased Bayer lands and somewhat until agricultural land which inappropriate use of this land shows in order to the agricultural. That this is the desertification progress in the region. Generally desertification process in this period years 27 has been a growing trend.Therefore multi-temporal and multi-spectral satellite data for enhancement, especially for desertification monitoring was large capability and classification after comparison method is helpful for determine the type and direction of changes occurred. Since the development of desertification, limited to a small area and is not recommended range is therefore more effective, in addition to work sheets, other sheets around the area also evaluate the process of desertification is to allow for planning and management in the field of combating desertification exist.
