Sensitivity Estimation Rock Units to Erosion by Using of Multi Linear Variation Methods. An Example from Lateshur Watershed, Northeast of Pakdasht

Lateshur watershed is located in northeast of Pakdasht in the Tehran Province and has surface area more than 22.2 km2. Hezardareh Formation, Neogen red beds and Quaternary alluvium crop out in this watershed. A dam has been built at the downstream part of this watershed that half of this reservoir dam filled with sediments during 12 years period. This subject caused lots of problems for the villages and agricultural lands in the downstream of watershed. This indicates that the rock units exposed in the upstream can produced a huge amount of sediments. We calculated the rates of sediment yield deposited in the reservoir of Lateshur dam with topographical maps during the period of 1993-2005. We used clay minerals as a tracer and multi linear variation methods for calculating of sediment yield from rock units. Based of clustering and F test, montmoriolite and illite are determined to be tracers. Finally, we conclude that marly member of Neogen red beds are the most sensitive rock unit to erosion and produced more than 97% of sediments yield that have been deposited in Lateshur dam reservoir.