Research On The Character Of Manning Resistant Coefficient And The Influence Factors In Andamu River

Manning coefficient is studied by using theory of hydrodynamics and one of the most important parameters to simulate the surface runoff. The research of manning coefficient have important practical significance,such as improving the flow washout for the slope erosion situation,researching the soil and water erosion and adopting the right slope of soil and water conservation measures. The test site is located in Beijing Andamu River. We picked out the bare land, the Pennisetum, Vicia, Artemisia, Bryophyta,the litter coverage and the gravel coverage, a total of 7 kinds of slope as the research object to study slope runoff velocity,the manning coefficient, the change of water and sediment yield in the kinetic parameters and correlation analysis of each slope roughness coefficient and its influencing factors by scouring experiment. The experimental results show that:1. When the flow rate increased from 5 ml/s to 30 ml/s, the surface velocity linearly rising trend,the velocity of Pennisetum slope is minimal and the bare land slope is the largest, the most obvious growth trend of velocity is the Bryophyta slope; when the flow rate is 5 ml/s,the manning coefficient of the litter coverage slope is the largest and the bare land slope is the minimum. The bare surface covered with gravel, have very little effect on the slope surface roughness coefficient.The Re is between 32.33-33.90,the Fr is between 0.85-6.50, the Darcy-Weisbach resistance coefficients f value between 6.48-376.17 and the f of the litter coverage slope is the largest and the bare land slope is the minimum.2. Roughness coefficient and erosion was negatively correlated, the Manning coefficient and the soil stable infiltration rate was positively correlated; four kinds of slope soil in filtration intensity by comparison to the Pennisetum> Vicia> Artemisia> bare land. The manning coefficient of slope surface can be used to indirectly said the soil strength, resistance to corrosion on the surface of the earth to see herbs to control slope soil erosion play a good role, including the Pennisetum effect is best.3. When the slope of 15°and 35°, the roughness coefficient decreases with the increase of runoff, when the slope approaching 25°, the roughness coefficient rises with the increase of runoff. When the flow discharge and slope gradient increasing, the change process of the Pennisetum slope velocity as the "first decreased and then increased"; Vicia slope as the "increase" and the Artemisia slope as the "first decreased and then increased".4. The Pennisetum improvement effects on slope soil was the most obvious, Vicia slope followed by and the Artemisia slope is the worst. The manning coefficient and vegetation coverage, soil organic matter content, capillary moisture capacity, capillary porosity, the drag coefficient Darcy-Weisbach f has positive correlation and there is a negative correlationg between the manning coefficient and soil bulk density, slope, flow rate, soil erosion rate,and Re. Manning coefficient and Darcy-Weisbach resistance coefficient f was a significant positive correlation.