Environmental Assessment of Bioengineering Techniques for River Bank and Slope Stabilization

Zanjan River is one of the main branch of Ghezel Ozan River which most of cultivated lands in Zanjan province are located around it. The depth of sediment in some area around the rive is about 30 meters and due to flood condition on this river, water have eroded riversides and have destroyed agricultural farms and caused the river to become meandrous. Due to economic and environmental aspects in river engineering works, a suitable method for protection of riversides is bioengineering which uses plant roots to stabilize riversides. Thus, this study has focused on mechanical strength of plant roots in this area to protect riversides from water erosion. In this research, the native plants of riversides were studied and the tensile resistance of their roots was measured in laboratory. The distribution and depth of penetration of roots were determined and shear resistance of soil with and without roots was measured and compared. The results of this experiment show that tamarisk and elm trees increased the shear strength of soil up to 30 – 50% in riversides. With respect to characteristics of these trees, it is possible to use these trees to stabilize riversides of Zanjan River. Tamarix, Populous Euphratica and willow trees with local reduction of water speed increased sedimentation in riversides with respect to characteristics of these trees it is possible to use them in biotechnical projects of riversides.