پديد آورندگان :
خبازي، مصطفي نويسنده استاديار جغرافيا، دانشگاه كرمان , , سيف، عبداله نويسنده استاديار دانشكده علوم جغرافيايي، دانشگاه اصفهان , , شيرواني، كورش نويسنده استاديار مركز تحقيقات كشاورزي و منابع طبيعي اصفهان , , نوحه سرا، مريم نويسنده كارشناس ارشد جغرافيا و برنامه ريزي شهري، دانشگاه آزاد اسلامي- واحد نجف آباد ,
كليدواژه :
كرخه , كواترنر , مآندر , الگوهاي فرمي , دشت سيلابي
چكيده لاتين :
from the old times , rivers and their fertiles plains were the heart of social civilization creation. Khuzestan plain is a short high with a moderate slope in which Karkheh river is flowing. This river through the geology period ,exclusively, in the 4th period was overrunning and activating which most of the time deviated and run to the route or other routes. In addition to the displacement of cityʹs focuses,caused the pattern change of floodway. The methodology of this research is of,field methods and historical studies which is made based on systematic method. In this research in the period span of 33 years, at first using of multi-spectrum pictures of Landsat satteliteincluding MMS pictures measured, ETM+, ETM in the years of (1975,2000,2008),numerical data 1/25000, topographic maps, GIS technique and also GPS take action to recognize the initial routes and old routes of karkhe river. After that, by means of old historical texts such as Ebnebatute, Ebnebalkhi, Ebnehoghal,andEstakhri the old-routes of the river were remade. In the next step, using far-distance measures, the meander of the river was reloaded and reembossed. The results of this research, caused to identify 4 main old-routes with many secondly routes (66 NO). Although it was in the case that entreaty of the river extracted from satelitte pictures in 1975 and with river route in 2008 were fallen to each other and was presented the route changes through 33 years in the form of route change map of Karkhehriver.
Key words: Floodplain,Meander, Quaternary,form pattern,Karkheh
Introduction
From the point of dealing view the river is very important for the geomorphologists and also from many aspects such as geometrical form of floodways,hydrolic and with space pattern. Therefore, considering morphology and changing in the form rivers are very important in the sight of morphologys. Rivers as open-systems through different periods are suffered many changes and alwaays exist from their primary routes and turned to the other routes. It seems that the repeated of route change of rivers in the 4 periods were related to 3 factors: 1)changing the main level of the river ,2)climate changes and 3)techtonique. The KarkhehRiver by settling down in theflood plain of Khuzestan was not excepted from this principal and always was changing from its main routes.
Materials and procedures
the methodology of this research is made based on the compounding of library,field methods and historical studies and systematic method. in this research in the period span of 33 years,at first using of multi-spectrum pictures of Landsatsattelite including MMS measured pictures,ETM+,ETM in the years of (1975,2000,2008),numerical data 1/25000, topographic maps ,GIS technique, and also GPS take action to recognize the initial routes and old-routes of Karkhehriver. Then by means of old historical texts such as Ebnebatute, Ebnehoghal, Ebnebalkhi and Estakhri the old routes of the river was remade. in the next step ,using the far-distance measures the Meander of the river was reloaded and reembossed.
Results and discussions
theKarkheh river because of slope decreasing and changing the sediments kind after Karkheh dam suffered many changes after arriving to Khuzestan plain. This old routes which are almost like a horseshoeʹs form extracted from the compounding’s of 2,4,7 bands and specified it by encoding pictures (7,12 shapes) comparing this picture with pictures of 1975 shows many specific changes through 33 years which defines motivating and activating of the river in the present period.
Conclusion
Rivers are dynamic systems that are changing continously. One of the geomorphic evidences of changing the river routes is Meanders which actually are important feature of environmental changes and specific signs of changing in the river-bed of water flowing. Karkheh river as 3th most biggest river of Iran after karoon and dez through its history sufferes many changes. On this base,historical studies and satellite pictures take action to identifying the old-routes of the river. Results of this research around the river showed 66 numbers of abondoned Meanders (7,15 shapes). 4main
routesare identifying:
1)the first old-route was branching off zoghae river and was connecting to river from north-western to south-eastern under the sand hills.
2) other 2 main routes was branchig off Dowirich and arriving to HoorolAzim. 3) fromhoorolazim to the down of main routes. one of them was flowing to the east of plain and the other to the south which connected together and were arriving to Arvand river.
4) another old-route was arriving to low-high area of Khuzestan plain from the west of Hoorolhoveyze and connected to Arvand river.
