Effect of Vetiver grass root system on river bank shear strength parameters, case study: Kor river

River bank erosion imposes sever damages to the adjacent lands annually and changes the river morphology considerably. In this study, the effectiveness of the Vetiver grass root system in enhancement of the soil shear strength and reducing the river bank erosion is examined. Several experiments were carried out to find the effect of Vetiver grass root system on soil cohesion and internal friction angle. Also, variations of morphological characteristics of Vetiver grass root system including RAR, RDR, RDDI and RLD in different depths have been investigated as well as the lateral and vertical distribution of roots. Three different spacing between Vetiver grass plants have been studied and the optimum distance has been proposed. The results showed that Vetiver grass root system increases the soil cohesion and internal friction factor upto 104% and 83%, respectively. Also, it was found that soil cohesion and internal friction factor are best correlated with RAR and RDR, respectively. Finally, an attempt was made to compare the Vetiver grass with several native trees. It was concluded that Vetiver grass is more suitable than common plants and can be considered as an alternative for river bank protection against erosion.