A Simulated Study About Runoffand Sediment Transportation On Channel Of Loess Plateau Small Watershed

The Loess Plateau is composed by fragmentized watershed, which is the sediment source of yellow river. The research about watershed runoff and sediment producing process and mechanism which can help us deeply comprehend the laws of Temporal-Spatial distribution of small watershed soil erosion, and it also can provide us the thoughts and data about small watershed erosion prediction model and soil and water conversation measures. Presently, there are masses of high-level research results about soil erosion of slope and channel system. Therefore, there isn't a perfect answer for this problem because of its complicacy. Especially, there is serious differences point of view to resolve the above problems, such as producing source of sediment and soil erosion controlling strategy. And so, we partition the small watershed to the both of slope and channel first time, and, we can research runoff and sediment transportation laws of channel by using small watershed normal model. The experiments include three parts as follows:1. Research of watershed model rainfall stimulationBased on the model experiment, using the combined methods of vector software and splash methods, the rainfall characteristics parameters were analyzed such as rainfall intensity of watershed model, the diameter median of raindrop, the raindrop sampling, the rainfall energy, and we got rainfall intensity at different spray nozzles composed and head pressure, we also got raindrops median diameter and entire rainfall kinetic energy at different rainfall intensity. It provides basis to research the simulation of runoff and sediment transportation at Loess Plateau small watershed.2. Runoff of small watershed channelFor past research methods, however, there are some shortcomings about rainfall simulation of runoff and sediment transportation research, and it also has shortcoming about plot observation data and the hydrologic data analysis methods of the entire watershed. And so, we carry on our experiments on small watershed channel, they were analyzed such as runoff and flow concentration of watershed channel, the relationships between channel rainfall infiltration and rainfall intensity. We convert the experiments data to the prototype, the results comparing with slope runoff show that: the channel runoff and flow coefficients are large than slope's, and the channel runoff is the slope runoff 1.14~1.2 times.3. Sediment transportation of small watershed channelBased of small watershed model of kangjia gelao gou, yangou at yan'an. Using rainfall simulation to research the channel sediment transportation, we got the relationships are aI bwhich between rainfall intensity and average sediment concentration and sediment yield transportation and modulus of erosion. The channel sediment concentration is the slope's 3.17～4.33times, the modulus of erosion is the slope's 3.78～5.10 times. We convert the channel sediment producing process to the prototype by using similarity scale. Comparing with past observed rainfall erosion data of phonotype, the results show that: the converted changing process of sediment production and concentration is consistent with prototype, and it can show the two changing process accurately. But the sediment concentration reducing process isn't consistent of the prototype's, and we got theoretical sediment transportation process of prototype channel which was corrected.