| On the basis of consulting a large number of literatures domestic and aboard, thepresent situation and latest development of hydrodynamic characteristics of overlandflow and slope erosion dynamic process were reviewed. In the paper, firstly, aiming atrevealing dynamic mechanisms of soil erosion process on steep slope, with acombination of theory analysis and simulated experiment, hydrodynamic characteristicsof sheet flow on steep smooth slope, and the effect of slope gradient, flow depth(flowdischarge) and rainfall on hydrodynamic features of sheet flow were studied. Secondly,runoff scouring experiments were used to study the rate of runoff sediment transport onLoess slope, the distribution of sediment delivery in different duration, and the variancelaw of runoff hydrodynamic characteristics over scouring time. Thirdly, based on theprinciple of roll wave superposition along downslope, the formation mechanism of steppool (or little erosive pole) was discussed preliminarily. And the conception of runoffscouring energy consumption on slope was posed to study the relationship betweenrunoff detachment rate and runoff energy consumption. Lastly, the critical energyconsumption condition of rill erosion initiation was illustrated. The main results arelisted as follows:(1) Based on the principle of saline solution tracing, an instrument for measuring thevelocity of sheet flow on slope was developed successfully, which afforded an effectiveexperimental ways to study the mechanisms of soil erosion processes.(2) The results of runoff experiments on steep slope showed that, except for a initialcertain slope length, the hydrodynamic characteristics of sheet of flow on steep smooth slope,including flow velocity, resistance and flow energy consumption, etc, didn't change withthe slope length. The flow velocity, resistance coefficient and energy consumption ofsheet flow on steep smooth slope increased with the flow depth( flow discharge) and slopegradient, while there was little effect of slope gradient on the Darcy-Weisbach resistancecoefficient.(3) The results of rain-affected runoff experiments on steep smooth slope indicatedthat, the velocities along downslope of sheet flow were more influenced by the raindropsplash, of which the influencing degree was determined by runoff discharge, and rainfallintensity. The raindrop splash would accelerate the velocity of shallower flow, and thehigher rainfall intensity, the greater the amplitude of flow velocity. The simulated rainfallwith median or lower intensity didn't have remarkable effect on the velocity of the runoffwith a larger discharge, while the rainfall with a higher intensity could slow down thevelocity of the runoff.(4) Sheet flow on steep smooth slope was no longer a stable uniform flow, butmoves in the form of roll waves. The flow with a form of roll waves on steep slopeWSed continUOusly along dOwnslOPe, and the nUmbe of roll wavs decreased at thesam time. Mly SPealdn the sloPe peent and twl intensity had littIeitw on the SUWsnion of roll waves aion downslOPe.(5) The twhInent rate ofrunoffon stmp sloPe bo with the flow dePth, andit mp't eduened aPParendy by sloPe gradint. The process of runoff erosion andwt yteld could be divided into three StageS, tha is, inboll erosiOn, rill forhation,rilI habIhation. Results shOWed thaL during the Process of runoff erosion on sloPe, theaInOUn ofrunofferosion and wt yteld in the Stag of rill theation accounted fOr 52~75 PerCeni of the total erosion amoun in the expemen' At for the flow veocityW with the scourin tiIn, and then becam more and more stable.(6) In nds M for on the Wsition theOry of roll waves aiong downslOpe,the fonnaon wtsm of mp POO on slope was discussed. Because of the rolI waves.rosnion, hal bo of fiow dePth cause the local shear thess tO boW Locai intenSe nmofferesion reSulted in the formatin of SteP POOls on sloPe:: (b;f W to the law of M conservation, the wtatin eqtalon of a... |
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