Research On Hydrodynamic Response Processes Of Soil Detachment Capicity Of Rill Flow On Loess Hillslope

Loess Plateau of China is the most serious soil erosion areas in the whole world, theserious soil erosion problem has not only damaged the ecological environment of the area, butalso posed a deadly threat on the lower Yellow River. Rill erosion is one of the mostimportant soil erosion processes and the significant source of sediment yield in the LoessPlateau. Soil detachment capacity of rill flow is the important parameter to the control of soilerosion severity, and it largely depends on the role of rill flow dynamic. So clarifying thehydrodynamic process of soil detachment by rill flow on loess hillslope could not onlyrevealing the mechanism of rill flow detachment and lay the solid foundation for rill erosionprocess model, but also it could promote the further development and perfection of erosiontheory and provide an scientific basis for the management of soil and water loss on loesshillslope.Based on the analysis of related literature both domestic and overseas and investigationin field work about rill, the hydrodynamic response process of soil detachment capacity of rillflow on loess hillslope was studied by the flume test of rill. Analyzed the hydrauliccharacteristics of rill flow on loess hillslope, as well as the variation characteristics of soildetachment capacity of rill flow and the coupling relationships between soil detachmentcapacity by rill flow and hydrodynamic parameter. Based on this analysis, the process-basedmodel and factor model of rill erosion on loess hillslope was developed, and it could provideeffective help for the development of the process-based model of rill erosion on slope surface.The main conclusions are as follows:1.The hydraulic characteristics of rill flow on loess hillslope was studied: Rill flowvelocity could be well described by a binary power function of flow discharge and slope, aswell as rill flow depth, Reynolds number, Froude number, shear stress and unit energy,resistance coefficient of rill flow could be well described by a binary linear function ofdischarge and slope; Flow discharge is the main impact factor to flow depth, resistancecoefficient and Reynolds number, however, slope is the main impact factor to Froude number;The rill flow regime was turbulent and pattern was rapid flow under the stated experimentalconditions.2. The variation characteristics of soil detachment capacity of rill flow was analyzed: Soil detachment capacity of rill flow increased with flow discharge and slope increased, therelationship between soil detachment capacity and flow discharge could be well described bya power function, the relationship between soil detachment capacity and slope could be welldescribed by a logarithmic function. The factorial model for soil detachment capacity withflow discharge and slope was found to be a linear function: Dc=-1.389+0.0612S+779.9709q,flow discharge is more influential than slope.3. The coupling relationship between soil detachment capacity of rill flow andhydrodynamic parameters was revealed: Soil detachment capacity of rill flow increased aseach hydrodynamic parameter increased. Under different flow discharges, with the increase offlow discharge, the response relationship of soil detachment capacity to velocity turn frompower function to logarithmic function, as well as unit stream power, stream power and unitenergy, while the response relationship of soil detachment capacity to shear sterss turn fromlinear function to logarithmic function; Under different slopes, the response relationship ofsoil detachment capacity to velocity could be well described by a power function, as well asunit stream power and unit energy, while to shear stress is an exponential function, to streampower is turn from power function to exponential function. Under different flow dischargesand slopes, the response relationship between soil detachment capacity of rill flow andvelocity could be described by linear function, as well as shear stress and unit energy, whileunit stream power and stream power were power function.4. Based on the analysis of hydrodynamic parameters of soil detachment capacity by rillflow, the mechanism and dynamic model of soil detachment capacity by rill flow wasilluminated and established. Stream power is the best hydrodynamic parameters to describe thedynamic process of soil detachment by rill flow under the experiment condition. Streampower is also the driving force for the occurrence and development of soil detachment by rillflow in the experiment. The dynamic model of the soil detachment capacity is the powerfunction of the soil detachment capacity in response to stream power, which is: Dc=0.4794W0.9043.