Study On Hydrodynamic Characteristics Of Riverside Rivers In North River

Influenced by the interaction effect of human activities and natural factors,the soil and water conservation function of the riparian zone is facing to serious degradation.Based on the field runoff souring experiment on the red soil slope in the riparian zone of the Beijiang River,this study analyzed the changes in hydrodynamic parameters and their relationship with erosion and sediment yield under different slope gradients(7°,9°,11°,15°)and vegetation coverage(0%,25%)and flow discharges(15 L/min,12 L/min,9 L/min).The results showed that:(1)The runoff rate of two vegetation coverage increased at first and then maintained stable with the increasing water release duration,the runoff rate increased with slope,while there was a significant power function relationship between 25% vegetation coverage and slope(P<0.05),the runoff rate increased with discharge volume and presented significantly positive with flow discharges(P<0.01).The sediment concentration of two vegetation coverage decreasing trend with the increasing water release duration,there was a significant linear relationship between bare slope and slope(P<0.05)and presented significantly positive linear correlation between 25% vegetation coverage and slope(P<0.01).The sediment concentration of bare slope increased with discharge volume and presented significantly positive with flow discharges(P<0.01).The relationship between sediment concentration and water discharge of 25% slope vegetation coverage was not obvious.The sediment yield of two vegetation coverage decreasing trend at first and then maintained stable with the increasing water release duration,the relationship is consistent between sediment yield and runoff sediment concentration.(2)The Reynolds number of two vegetation coverage increased little with increasing discharge time and its relationship with slope was not significant,which indicated that slope gradient had no regular effect on the Reynolds number.The Froude number decreased firstly and then tended to be stable with the increase of the water release duration and the average Froude number of bare slope was greater than 1 in all treatments,which demonstrated that overland flow was in a state of torrent and presented significantly positive linear correlation with slope gradient(P<0.01).The Froude number of 25% vegetation coverage increased initially and then decreased with slope,inferring that there could be existed nonlinear relationship between Froude number and slope gradient.There was no significant relationship between the Froude number and the amount of water release.The flow shear stress of bare slope increased at first and then maintained stable with the increasing water release duration,the water flow shear stress on the slope is almost a straight line under 25% vegetation coverage.the flow shear stress increased with slope and presented significantly positive with slope(P<0.01),and presented significantly positive linear correlation with flow discharges(P<0.05).The relationship is consistent between flow shear stress and stream power.(3)The soil erosion rate of two vegetation coverage increased with Reynolds number and presented significantly positive with Reynolds number(P<0.01).The soil erosion rate of bare slope increased with Froude number and presented significantly positive with Froude number(P<0.01),There was no significant relationship between the Froude number of 25% vegetation coverage and the amount of water release.The soil erosion rate of two vegetation coverage increased with flow shear stress and presented significantly positive with flow shear stress(P<0.01).The soil erosion rate of two vegetation coverage increased with stream power and presented significantly positive with stream power(P<0.01).