Investigation of Stabilization of River Margins with use of Biological method for prevention of soil Erosion and sediment production

ABSTRACT: Investigation of the effect of plant species and planting pattern in combination with nonstructural mechanical methods in decrease of erosion of river margins are some cases which can be studied as case projects for the state famous rivers. In this research bioengineering method is executed for biological fixation of river margins in arid and semiarid areas for investigation and introduction of the most proper biological method with a view to plants compactness and combination. First with recognition of the place of project execution the rivers of the area were visited and after visiting a few basins, Jomebazaar River was selected. Then river margins become sloped and vegetation was executed in the river margins with 7 foreseen units including A) trees with distance of 2X2m, B) shrubs with distance of 1X1m, C)Bush, D) Combination of trees and bushes with distance of 1X1m, E) Combination of trees and bushes with distance of 1X1m for bushes, G) grassy species, F) Control unit (Erosion severity and type are dependent variables and plant species, annual growth, plant compactness and combination independent variables in this research). The plants, which are cultivated as vegetation, include alder, grass and shrub vegetation. Shear resistance of the soil containing alder roots was tested and calculated by direct shear device. The results of tension test showed that maximum tension residence of alder samples is 42.82 mega Pa. In the third sampling, erosion in grass and bush was 110, in trees 90m in shrubs 100, in the three tree, shrub and bush 40, in the two bush and shrub 70, in the two tree and bush 60, in the two tree and shrub 80 cubic meters per hectare that we can observe the role of vegetation and biological fixation on decrease of erosion volume in the research area. The selected vegetation besides soil protection showed good results with a view to extension, survival and resistance against water flow and bending and can be advised for the most river margins in the province.