Above The Incoming Water And Sediment Erosion Process By The Impact Of The Pilot Study

An Experimental Study on Effects of Up-slope Runoff and Sediment on Down-slopeErosion ProcessGraduate: Xiao PciqingDirected By: Zhcng FenliAbstractSoil erosion at hilly-gully region of the Loess Plateau has obviously erosion vertcalzones from waershed boundary tO gUlly edge, i.e., sheet zone dominated, rill zonedominated, and shallow guly zone dominated. To quantify effects of uP-slope nmoff andsediment on downslope detachInent, deposition and tusport processes as wel1 asmechbosrns can provide boortanly scientfic bases for establishing erosion predichonmodel. A dual-box system (one is test box and the other is feeder box) is used to qUanifylinpacts of uPlope nmoff and sediment on detachmenL dePosition and tranSport Processesat downslope sheet and rill erosion dominated zone, and relation between ril1 erosionprocess and rill fiow hydrauic parameters. New progresses on above research field havebeen made. The main resultS are as fOllows:l .A duai-box systCm of feeder box, located at the uP-slOPe, and test box lotaled thedownsloPe was designed, Which can control the test box receiving runoff from uP-sloPearea or noL and uP-sloPe nmff rate as well sediment concentration. TherefOre, thedesigned dual-box system resolves scientfic problem for studying on runoff with variablesedimed concentration effects on erosion process.2.Up-slope nmoff and sedhoent have signfican imPacts on downslope detachrnent,deposihon and transPort processes. For loose sdse Under differen rainfal intensities of50, 90 and l30wt, sediment frOm uP-slope discharging into down-slope is totallytranSported by down-slope runff UP-slope runoff causes additional detadrient at thedown-slope, and sediment regime at down-sloPe is detachInent and taport dominated.For compaCt surfaCe under rainfall intensity of 50Inm/h, erosion, deposition and traxisportprocesses occur simultaneously at down-slope, sediment regime is detachIneot, dePositionand transport dominated. As rainfall intensity increases from 50 ITunlh to 90 and l30 ed,sediment regime at down-slope is erosion-transport dominated.3. Net sediment delivery caused by up-slope runoff is an indicator to quanify effectsIIIof up-slope runoff and sediment on down-slope sediment production. For the loose and compact surface treatments, the net sediment delivery (S) caused by up-slope runoff accounts for the total sediment delivery Sft at down-slope 72.4 to 92.7% and 45.5 to 83.7%, separately. Therefore, up-slope runoff is intercepted to infiltrate on-site is a key measure to control soil erosion at billslopes.4.The net sediment delivery (S) at down-slope caused by up-slope runoff increaseswith an increase of rainfall intensity or runoff from up-slope, and with a decrease ofsediment concentration in up-slope runoff. In addition, nil erosion development and soil bulk density have great effects on the net sediment delivery (5). Sediment delivery during the run is associated with active nh head-cut advance.5.For dli channel at down-slope, sediment regime is always detachment and transport dominated. The net sediment delivery (S) caused by up-slope runoff increases with a decrease of sediment concentration in up-slope runoff. Meanwhile, The net sediment delivery (S) increases with an increase of rainfall intensity and runoff xate from up-slope. The relation between the net sediment delivery (S) and up-slope runoff is described as a positive index function.6. As compared to without feeder input at the ru box, up-slope runoff discharged intothe ru box causes that <0.001mm particle size (clay) in erosive sediment increases, and0.05-0.001 mm particle size (silt) decreases. The clay content increases with an increase of rainfall intensity or runoff rate from up-slope. Meanwhile, clay content in erosive sediment increases as increase of ru flow velocity and nil sediment delivery.7.Up-slope runoff and sediment have important effects on dli flow hydraulic parameters, such as dll flow velocity, Reynolds number...