Investigation of Effect of Vegetation Cover on Soil Erodibility of River Banks

Abstract

The effect of vegetation cover (VC), in addition to environmental changes, is one of the most critical aspects affecting the erosion of the soil of river banks. Therefore, this paper investigated the influence of vegetation cover (VC) on the erosion of Tigris River banks in Samarra City. The study was conducted with multiple monthly research periods (May, June, July, and August) during the summer of 2021for testing the soil erosion in twelve sites on Tigris River banks. A mini jet erosion test (mini JET) device was used in this work to reduce testing times, save energy, and provide a low cost method. At each site two JETs were conducted, one on a soil covered with vegetation and other on a bare soil. The monthly average values of the soil erodibility coefficient (kd), the critical shear stress (τc), and the percentage of VC (VC%) were computed for the soils with VC and the bare soils at each site. It was concluded that improvement of soil erodibility resistance could be achieved by the existence of VC due to an increase in soil organic matter (OM) content. It was noted that the kd had more decreasing with the existence of VC compared to the bare soils at the twelve sites, while the τc showed more increasing. It was also discovered that the lowest value of kd (= 0.4 cm3/N. s) occurred at a VC% of 32.2% at site no. 12. The findings of this study supported the results obtained from previous researches which studied the effect of VC on bare soils. Finally, the study recommended that the VC% on the Tigris River banks within Samarra City be more than 32.2% to reduce the erosion of river banks as well as to preserve the morphology of the river