Mohammadmehdi Hosseinzadeh; Somayyeh Khaleghi; Faraz Vahedifar
Volume 4, Issue 10 , June 2017, , Pages 145-164
Abstract
The bank erosion is the dominate phenomena in the Qaranqoo Chai River, upstream of Sahand dam, at this time of the year leading to changes in river, increasing the radius of curvature at the bends, and straight channel widening. Consequently, it damages the land and the river's facilities and causes ...
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The bank erosion is the dominate phenomena in the Qaranqoo Chai River, upstream of Sahand dam, at this time of the year leading to changes in river, increasing the radius of curvature at the bends, and straight channel widening. Consequently, it damages the land and the river's facilities and causes numerous changes in the pattern of the river, sediment production, and sediment transfer to Sahand dam. In this research, a Bank Erosion Hazard Index (BEHI) was used to evaluate annual bank erosion in the Qaranqoo Chai River. To this end, 9 cross-sections were selected and some parameters such as bank full width, average bank full height, root depth, root density, bank angle, surface protection, bank material, and bank stratification were measured. The results of the BEHI method showed that both of the right and the left banks were eroded and that the erosion risk was moderate to very high in all of the right bank's cross sections except its cross-section 4 which had a very low erosion risk. In addition, the erosion risk of the left bank's cross sections were very low to extreme. Indeed, due to the low root density and loose material, the right bank's cross-sections had higher erosion risk than those of the left bank. Moreover, the erosion risk was reduced in the middle of the river because its root depth was higher than the banks' root depth. Indeed, BEHI incorporates bank variables that are factors in entrainment, surface erosion and mass erosion. These variables are bank–height ratio, root–depth ratio, weighted root density, bank angle and surface protection. Variables have empirical values that are, in turn, converted to index values and summed for a total BEHI score. Scores are adjusted by bank material and bank material stratification. BEHI scores are then categorized by erosion potentials. A greater score indicates greater erodibility. Bank height is the distance from bank toe to the top of the bank.
