Ardak Watershed with an area of about 497 km2 is one of the tributaries of Kashaf Rud River Watershed in north east Iran, which consists of two main rivers. This catchment is located in the Kopet-Dagh structural zone and Ardak Watershed is surrounded by Chaman Bid, Mozduran, Shurijeh, Tirgan, and Sarcheshme Formations. The lithofacies and architectural elements show that two main rivers of this watershed are gravel-bed braided river in their most parts. The major erosion types in this watershed are rock fall, rill, surface erosions, and gully and channel bank erosion. In the study area, the amount of sediment yield estimation in GIS framework using MPSIAC model is about 130.749 m3 km-2 yr-1 or 1.77 t.h-1 and most parts of the basin (more than 90%) has low erosional rate. Mozduran and Tirgan Formations are more resistant to erosion than other formations with maximum relief and gradient. The major factors for erosion and sediment yield in this catchment area including: annual floods especially in rainfall season, high sensitivity of lithologic units to mechanical erosion, high slopes of hillsides, and rock fall phenomena that they need suitable watershed management. Also, present of several villages in the vicinity of the main channel has increased understanding of suitable methods for flood hazards control. We hope this study can help in better understanding of erosion and sediment yield patterns of watersheds for better water and soil preservation and watershed management.

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