Study of Fractal Dimension Quaternary in Bijar Basin with Emphasis on Base level changes

Changes in the base levels are the most important factors of forms and processes’ imbalance in drainage basins. Ghezel Ozan basin, which is the sub-basin of Caspian Sea, has had many effects on base level fluctuations. In this study, Channels and Lithology were evaluated using GIS software and topographic and geological maps. Using evidences, the base level changes including the capture and diversion of convergent radial rivers and channels of Bijar geo-neuron in Qezal Oazan Basin were identified. Also, the relationship between branch and length of the channels in Bijar sub-basins was investigated using the fractal geometry theory and Horton- Strahler stream ordering method and their fractal dimension was calculated. The results show that the effects of changes in local base levels of Bijar hole can be traced as aggregate levels in the alluvial plains of 6 sub-basins of Angouran-Chay, Hassanabad Yasukand, Yol-Kashti, Ghorveh and Dehgolan, Garmab and Sujasrud. The prospecting process is visible in the center of the hole. At elevations of 1561, 1540 and 1515 meters in Bijar hills, 3 lake terraces have been observed. The fractal number of 2.12 of Bijar basin indicates that the whole basin is in a relatively moderate condition and the retardation erosion in the branches is going to be stopped. In the two sub-basins of Yol-Keshti and Ghorveh-Dehgolan, fractal dimension of less than 2 shows that the coefficient of branching is greater than the basin area. At the head of the water at the Angoran Chay, Sujasrud and Garmab sub-basins, the branches are still developing and retreating. Hassanabad Yasukand sub-basin with the highest fractal number among the sub-basins (3.25) reaches its maximum balance and the lowest erosion is dominant in its branches. Investigating the relationship between fractal dimensions and branching ratio with the area of the studied basins indicates a reverse and negative relationship.