Comparing Susceptibility of Marl Lands to Erosion Using Rain Simulator in Zanjan Province

Marl formations cover about 4438 km sq. (ca. 20%) of total surface area of Zanjan province. In this research، susceptibility of marl lands to water erosion was studied using a rain simulator. In this regard، by overlying slope، climate، and marl units of geological formation maps، a number of 18 homogeneous units were distinguished using ArcGis 9. 3 software. Besides، during field operations، runoff within 1*1 m. plots were recorded within each homogeneous unit by using a rain simulator. A total of 54 plots were tested، and the data collected from field operations were analyzed on the basis of randomized complete block design with factorial treatment structure، General Linear Method (GLM Model) procedure، F Test and Duncan Multiple Range Test. A study on the relationship among the amount of sediment yield، volume and run-off coefficient of marl unit showed a quadratic regression equation to express the variations. Statistical data analyses showed the significant effects of the marl units، slope، and climate on the runoff threshold (p<0. 05). Marl units could be classified into four groups based on the amount of sediment yield:، marls of Pliocene (PL) and lower red (OL) in one group، while upper-red (Mu)، Qom marl (OM)، and Eosen (EM) marl units each in a separate group. These 4 groups differed significantly from the view point of the amount of sediment yield due to the physico-chemical differences among them. In these units، having more silt content resulted in more sediment production. This is because silt particles do not stick together and break up upon wetting، thereby can be easily transported. This investigation suggests that the combined effects of slope and climate have significant effect on the amount of sediment yield.