Study and comparison of erosion and sediment yield in sub basin of Veladareh catchment (Ardabil province)

Extended abstract:
1-Introduction
 Veladareh basin is located in the eastern site of Sabalan volcanic massive and north of Sarein town in the north west of Iran. The length of Veladareh River is 37.75 kilometer and its drainage basin area is 37.3 square kilometer. This basin is part of Qaraso and the Arax river basin. Veladareh basin is located at 38° 10' 17" to 38º 13' 21" northern latitude and 47º 58' 10" to 48 º 9” eastern longitude. The purpose of this study is investigation of erosion and sediment estimating in the Veladareh basin.
 
2- Methodology
 Aim of this study is estimation of erosion rate in the Veladareh basin. For arrive to above aim the Veladareh basin was divided to four sub-basins. Erosion rate was estimated on one of the sub basins using by Erosion Potential Method (E.P.M).
 
In order to perform a conservation soil and nominate struggle methods with erosion and decrease of sediment yield must be estimated total volume of yearly sediment rates. To achieve this goal estimated 4 erosion factors include Erosioncoefficient of basin (Ψ), Land use index (), Susceptibility of rocks to erosion) Y) and mean gradient of basin (I) in the four sub basins.
 
 3– Discussion
Base of four above agents we are estimated Erosion intensity coefficient from formula 1 in the work units (Refahi, 1375: 257).
Z = Y.  (Ψ+  ).
Just as show in table 3 and fig. 6, erosion intensity coefficient is different between .62 in the north Erdymosa catchment and .77 in the Arandareh catchment. Between the four above effective agents role of gradient is higher than others agents, that is caused erosion intensity is different in this basin. Erosion intensity in Arandareh catchment has 2 erosion classes and in the others sub basins have 3 erosion classes. For estimate of yearly especial erosion in E.P.M method is used fomola2 (refahi, 1375: 259).
 =  T. H . π .
Just as show in table 4, especial erosion in the whole Veladareh basin is 777.7 m3/km/y or 10.3 ton per hectare. Arandareh catchmen between sub basins has higher especial erosion (1099 m3/km2/y or 14.3 ton per hectare) than that others catchments, because of high branching ratio, high erosion coefficient and high gradient; but Erdymosa catchment has lower especial erosion(660 m3/km2/y or 8.6 ton per hectare), because of low gradient. To estimate of annual erosion rates in basin area is used formola4 (Refahi, 1375: 261):
Just as show in table 4, whole basin can produced 29008 m3 sediments during year. The highest produced sediment was related to Arandareh catchment (10331 m3/y) because of setting in mountainous area, high gradient and high area (9.4 km2). The lowest rate of produced sediment was in north Erdymosa sub basin (5676 m3/y), because of gentle gradient and low area (7.8).
 
4– Conclusion
 Conclusions of study show that violence of erosion is intense in Arandareh subbasin (upper part of the basin) due to high gradient in this part.
But in the lower part of basin (Veladareh, Erdymosa and north Erdymosa subbasins) rate of erosion is low; because in this part gradient is few. Rate of especial erosion in whole of basin and per catchments of Arandareh, Veladareh, Erdymosa and north Erdymosa in order to arrange have been calculated 10.3, 14.3, 8.7, 8.6 and 8.6 ton in hectare in year. Potential of sediment discharge in whole of basin and sub basins in order to arrange have been estimated 29008, 10331, 7912, 5676 and 5179 cubic meter in the year. Excessive of especial erosion and potential sediment discharge in Arandareh catchment, than others sub basins is much of gradient and susceptibility of rocks.  Whereas in the others catchments (Veladareh, Erdymosa and north Erdymosa) factor of gradient decrease effect of others agents in viewpoint of sediment yield and have been decrease a potential sediment discharge in these catchments.