Study of the Rate of headcut and sediment volume Erosion in Channels with Steep Slope

Subject Areas : Farm water management with the aim of improving irrigation management indicators

امیررضا سالمیان ¹ , mahmood shafai ² , امیر خسروجردی ³ , حسین بابازاده ⁴ , حسین صدقی ⁵

1 - faculty member
2 - faculty member
3 - عضوهیات علمی دانشگاه علوم و تحقیقات
4 - عضوهیات علمی دانشگاه علوم و تحقیقات تهران
5 - عضو هیات علمی دانشگاه

Received: 2016-06-29 Accepted : 2016-08-20 Published : 2017-02-19

Keywords: erosion rate, headcut erosion, flume, bed slope, erosion volume,

Abstract :

Headcut erosion is a sudden change in height or slope that makes gullies and valleys and may change within a height ranged from less than one centimeter to several meters depending on several factors and upstream movement. Occurrence of headcut erosion phenomenon in the rivers will result in bed erosion and instability of beaches. As a result, the river is widened and the outcome of the phenomenon is the transfer of large amounts of sediment downstream and dams’ reservoirs. Five adhesive soil samples including, clay and silt with different mixture percentages were examined and tested for 25% upstream and 5% downstream slopes for discharge, velocity and depths of several flows in the study. Volume of the produced sediment was measured in terms of real time and average. In addition, headcut rate and sediment discharge were measured. Some of the phenomena observed in the study that played an important role in the production of sedimentation volume and headcut rate include occurrence of hydraulic jump at the junction of steep slope to mild slope, tensile cracks on the soil surface and increased slope of bed during the experiment due to erosion. According to the results, changes in the three parameters of the amount of silt, upstream slope and flow rate are directly related to the increased rate of movement of sediments and headcut velocity. In pure clay, by increasing flow velocity 1.5 times the average volume of sediments, 13% headcut velocity and sedimentation discharge increased to 40% and 21%, respectively. Moreover, 50% increase of silt increased the average sediments volume, headcut velocity and sedimentation discharge  by12%, 38% and 19%, respectively.

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