mohammad javad khangani

Many factors affect soil erosion and runoff generation. However, the role of some factors such as freeze-thaw (FT) processes has not been well considered yet. The present study therefore aimed to simulate and explain the effect of FT cycle on runoff generation and sediment yield under rainfall simulation condition. Towards this attempt, air and different soil depth temperatures were analyzed in natural condition and 10 cm soil depth was targeted for the soil laboratory experiments. A FT cycle with three and two days for freezing and thawing was taken place. The rainfall storm with 1.2 mm/min and 30 min duration was simulated and conducted for three treatments in soil erosion and rainfall simulation laboratory of Tarbiat Modares University. The results showed that the induced FT cycle soil had a distinct and significant behavior and different from that seen for the control plot. So that, the times of runoff generation in freezed and FT cycle treatments were 2.74 and 3.25 times less, respectively, compared to that reported for the control plots. The runoff volume and sediment yield were also respectively reported in turn of 1.46 and 1.16 and, 11.92 and 2.65 times more for freezed and FT cycle induced treatments compared to those recorded for control plots. Ice lenses and frost heaves plus creating situations close to soil saturation after FT cycle were the most effective factors in distinct behavior of soil induced by Freezingand FT cycle.