بررسي حساسيت به فرسايش پادگانه هاي كواترنر حوزه آبخيز طالقان

Erodibility of Quaternary Alluvial Terraces of Taleghan Drainage Basin, Iran

In this research Quaternary Deposits of Taleghan Drainage Basin were investigated, related map was provided and their erodibility was determined. The most widespread Quaternary Deposits of Taleghan Drainage are alluvial terraces which are as follows from the higher elevations to present alluvial river: " Mindel" Terrace," Riss" Terrace ," Wurm" Terrace ," Toria War" Terrace . The erodibility of alluvial terraces and alluvial fan deposits were investigated by different methods. For this purpose, in the case of" Riss" and " Toria war" alluvial terraces having thin soil horizon, modified -K parameter in USLE model and rainfall simulator were used. For " Mindel" and " Wurm" Alluvial Terraces and Jazan-Varkesh Alluvial Fan having thick soil horizon, K parameter in USLE model and rainfall simulator were used. The results of this research have shown that the most widespread Quatenary Deposit of Taleghan Drainage is " Riss" with 2743 hectars and 2.4% area. Alluvial Terraces are mainly found in the center of Drainage basin. The amount of modified K parameter in " Riss" Terrace is 0.12 and in " Toria War" Terrace is 0.17. The amount of K in " Wurm" Terrace is 0.23, in " Mindel" Terrace is 0.16 and in Jazan-Varkesh Alluvial Fan is 0.05, the order of erodibility from the highest to the lowest is " Wurm"," Toria War"," Mindel", "Riss" Alluvial Terraces and finally Jazan-Varkesh Alluvial Fan. The order of erodibility from the highest to the lowest according to rainfall simulator is: " Toria War", " Wurm"," Riss" and " Mindel" Alluvial Terraces and finally Jazan-Varkesh Alluvial Fan. In conclusion, except for very coarse-grained alluvial terraces in which there are difficulties in using rainfall simulator, the results from K parameter in USLE model and rainfall simulator are in accordance with each other.