The role of slope aspect in runoff and sediment production of Ghachsaran and Aghajari formations

Extended Abstract
Introduction:
The erodibility of watershed area is a function of several factor, one of these factors is topography. Including main topography features is slope aspect of which directly or with the effect on other environmental factors is caused changes in soil hydrological processes particularly the potential for runoff and sediment production. Soil erosion is the most important environmental factor in the world that adversely affects all-natural ecosystems as well as those under human management. Although soil erosion has existed throughout history, it has been intensified in recent years due to improper land use. Environmental factors, such as climate situation, topography, soil, and land use affect sediment formation in watershed areas. Aghajari formation is among the most erodible in Iran. Aghajari formation, covered with Bakhtiari conglomerate, is located on Mishan marl formation. This marl formation was formed between Pliocene and Miocene. Aghajari formation consists of gray and brown calcareous sandstone, gypsum red marl, and siltstone. Its main section spreads from Omidiyeh to the Aghajari oil field and it has a thickness of 2965 meters. The presence of gypsum marls has made Aghajari formation apt to erosions of different kinds, especially surface erosion, rill erosion, badland, and mass movement. One of the most eridibility of Iran is the Gahsaran formation. Gahsaran formation has oil industries that yearly thousands of tons of sulfur and carbon dioxide interpolate into the air. And it can be caused by acidic rainfall. Thus investigating the role of acidic rainfall on soil erosion and sediment production in these areas is necessary. Gahsaran formation has a thickness of about 1600 meters. A viewpoint of lithology is consisting of salt, anhydrite, colorful lime, and some shale. Gahsaran formation age is lower Miocene.
Materials and methods:
In this investigation in order to investigate sensitivity to the erosion and sediment yield the main aspect of slope of Aghajari and Gachsaran formation deposits, part of margha and kuhe gach watershed areas in Izeh Township respectively with the area of 1202 and 1609 hectares was elected. In this investigation in order to determine productivity runoff and sediment in 8 points and with 3 replicates in Gachsaran formation and in 8 points and with 3 replicates in Aghajari replicates in rainfall intensities 1 and 1/25 mm in min in 4 slope aspect; northern, southern, eastern and western with using of kamphorst rain simulator was done. In order to analyze statistical from SPSS and EXCELL was used. The study utilized the Kamphorst rainfall simulator. This fully standardized, easily portable rainfall simulator was designed to cover a plot area of 625 cm2. The rainfall simulator is used to determine the characteristics of soil, erosion, water infiltration, and is also suitable for soil research. It is a standard method to use it to determine the erodibility of surface deposits. The experimental plot area of 625 cm2 with a smooth gradient was selected, which was the representative of the main slope aspects. Meanwhile, the Kamphorst rainfall simulator was installed at the height of 200 cm to reach to raindrop boundary velocity.
Results and discussion:
The highest of sediment rate in both Gachsaran and aghajari formations in rainfall intensities 1, 1/25 mm in min is belonged to eastern slope aspects. The highest of runoff rate in aghajari formation is belonged to northern slope aspect and in Gachsaran formation is belonged to southern slope aspect. There was a significant difference in the south-east, south-west slopes in comparison of the amount of sediment produced in different aspects of the slope in the Aghajari Formation at the intensity of 1 mm/min. But, there was a significant difference in the amount of runoff produced and permeability of north-west slopes. And at 1.25 mm/min intensity, sediment production in south-east and south-west slopes showed a significant difference. But runoff was significantly different in north-south, north-east and north-west slopes. In terms of sediment production in Gachsaran and Aghajari formations, the total rate was highest at two intensities of 1 and 1.25 mm/min in the eastern slope. But, in terms of runoff in Aghajari Formation, the northern slopes have the highest runoff and in Gachsaran Formation, the southern slopes have the highest runoff. And, in terms of permeability in Aghajari Formation, the southern slopes and in the Gachsaran Formation, the western slopes have the highest penetration rate in the two intensities.
Conclusion:
The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.
Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formation
Conclusion:
The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.
Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formation
Conclusion:
The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.
Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formation
Conclusion:
The rate of productivity sediment also in Aghajari formation in both mentioned intensities is more than Gachsaran formation. But the rate of productivity runoff in mentioned intensities in Gachsaran formation is more than Aghajari formation. The rate of changes in productivity sediment and runoff in various slope aspects in both formations also significance difference showed.
Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formation
Key words: Soil erosion, Sediment production, Aghajari formation, Rain simulator, Gachsaran formation