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University of Mohaghegh Ardabili (2018)

Determining Effects of Structural Stability and Erodibility on Runoff and Sediment Production in Different Geological Formations of QarahShiran Ardabil Watershed

Asgari Hasanakloo, Ebrahim

Titre : Determining Effects of Structural Stability and Erodibility on Runoff and Sediment Production in Different Geological Formations of QarahShiran Ardabil Watershed

Auteur : Asgari Hasanakloo, Ebrahim

Université de soutenance : University of Mohaghegh Ardabili

Grade : Master Thesis 2018

Résumé
Soils formed on different rock base has some different characteristics in terms of runoff and sediment production based on the source minerals, structure of rocks, differences in their physical, chemical and mineralogical characteristics. In the same way, geological formations have different nature based on differences in texture, composition, resistance and sensitivity to erosion and sediment production, and the erodibility of various types of rocky and sedimentary units and the quantitative and qualitative characteristics of petrography and their physical and chemical properties. Different methods exist for measuring the amount of erosion, sediment and runoff produced in different formations, and the most common method is the use of a rainfall simulator. The characteristics of geologic formations and investigating the resistance of rock units to erosion are important in erosion and sediment and soil conservation studies. Considering the importance of this issue, in this study, the effects of structural stability and erodibility on runoff and sediment production in different geological formations of QarahShiran watershed in Ardabil province were studied using a rainfall simulator. In this research, the geologic formations with the same resistance coefficient to erosion were combined and then the sampling was done for runoff and sediment recording using a rainfall simulator and the soil samples were taken from 45 sampling points. Then the amount of runoff and sediment and parameters related to soil erodibility factor (K) were determined through laboratory experiments. The variations in runoff values in the samples range from 0 to 15.04 liters, sedimentation from 0 to 4.26 grams per liter, runoff threshold of 0 to 14 minutes, organic matter 1.91 to 5.28 percent, and the amount of erodibility (K) between 0.12 to 0.25 t ha h ha-1 MJ-1 mm-1. For comparison of geological formations in terms of erodibility, runoff, runoff threshold and sediment content, the One-way analysis of variance test was used. The results showed that there was no significant difference between geological formations of the study area in terms of erosion, runoff and sediment, but the differences of runoff threshold of geological formations were significant at 0.05 level. The results of the variations in the erodibility factor at the level of the area showed that the highest amount of this factor is related to the central and middle part of the study area, and the smallest values are related to the upstream or south and southeast parts of the watershed. The variations in the runoff threshold variablity had the lowest values in the upstream (southern part) of the study area and increases with an increaing trend in the geological formations of the lower (northern parts) of the QarahShiran watershed. The runoff values in the upstream formations of the field are high and decrease in the lowest parts of the watershed. The amount of sediment in the upper reaches of the watershed is lower but in the outlet and downstream of the watershed had the highest amount.

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Page publiée le 23 mars 2020