Investigation of sedimentology, trend of changes in grain size and determination of Debi-sediment equation in Jajroud drainage basin
Subject Areas :فرج االله Fayazi 1 , نیما Nezamvafa 2 , KH Rezaei 3 , ندا Norouzi 4 , فائزه Borbori 5 , محمد Nakhaei 6
1 - گروه زمین شناسی، دانشکده علوم، دانشگاه تربیت معلم تهران
2 - گروه زمین شناسی، دانشکده علوم، دانشگاه تربیت معلم تهران
3 - گروه زمین شناسی، دانشکده علوم، دانشگاه تربیت معلم تهران
4 - گروه زمین شناسی، دانشکده علوم، دانشگاه تربیت معلم تهران
5 - گروه زمین شناسی، دانشکده علوم، دانشگاه تربیت معلم تهران
6 - گروه زمین شناسی، دانشکده علوم، دانشگاه تربیت معلم تهران
Keywords: Flood, Jajroud, sedimentology, Debi,
Abstract :
Filling sediments behind dams decrease their useful lifetime, so sedimentological investigations in bedof arriving rivers are very necessary for distinguish and determination of sediment producer sources ofsediments. Latian dam and Jajroud river have a critical situation. Jajroud drainage basin has an extentabout 710 km2. It is located in north east of Tehran. It has 7 sub basins include Fasham, Ahar,Meigoon, Lavarak, Emameh ,Kond and Afjeh. Its shape is nearly ellipsoid from NW to SE. Thisbraided river has gravely bed with single channel and dam parameter more than 1. Average slope ofJajroud river is 4 percent. This river flows on bicarbonate, silicate, calcium bicarbonate, sulfate andsalt material as bed rocks. The size of bed sediments has very irregular changes due to specializedtectonic activities in this area, arriving minor branches, clastic inputs, and changes in slope. So densityof drainage in this river is 1.6. Most of sedimentary bars in Jajroud river are longitude and they showshallow and claim conditions. Morphoscopy of grains doesn’t have any defined trend. Granulometricgraphs are polymodal. Sorting of grains are bad mostly. The graphs of mean and median changes havenot regular trend. Most of samples have negative skewness and they are platykortic. Branch coefficientof this basin is 3.081, so this basin is general basin. The hydrograph curve of flood is normal. Finalmodel for Debi- sediment for Jajroud basin has calculated based on physiography factors of basin thatis correlated in maximum of Debi and flooding sediments by power ministry of Iran.
