| Due to the insufficient of soil erosion mechenism, in presented study, a more comprehensive research was carried out via comparative rainfall-runoff-erosion tests on slope of small scale, physical-based hydrological model, as well as the statistical method. This research made detailed discussions and analysises on the response characteristics of rainfall-runoff-erosion process in Loess Plateau region, based on a series of rainfall experiments with different characteristics combinations. The main contents of this dissertation are as follows:(1) Data from the previous rainfall-runoff-erosion tests in our scientific research group was systematically analyzised. The results showed that physical model tests of small scale in this study can effectively describe the hydrological response on slope in nature.(2) Physical-based hydrological model-Integrated Hydrology Model (InHM) can effectively simulate the runoff/erosion process. Especially, the hydraulic conduvtivity of surface soil acquired from those numerical simulations not only reveals the change of physical characteristics on surface soil, but also highlights the advantages of InHM to some degree, while comparing with the traditional hydrological models.(3) As for the runoff process, soil crust was commonly occurred during the rainfall events on slope. It is found that ranfall characteristics have significant effects on crust development characteristics, especially the rainfall moving directions along the slope markly influence the crust type and runoff stage. Soil crust is confirmed to be one of the main reasons causing the decrease of both porosity and infiltration, increase of runoff, advancing initial runoff time, as well as the change of runoff stages.(4) Soil erosion was significantly occurred coupling with runoff process and crust development. The sediment yield in succession rainfall events obviously decrease in our study. It is showed that the spatiotemporal characteristics of total sediment yield was mainly influenced by total rainfall and runoff stage, while that of peak sediment yield was mainly influenced by rainfall moving directions.(5) Analysis of erosive sediment grading showed that silt soil is likely to be most easily eroded. And the rainfall directions influence the erosive grading only in early rainfall stage. On the whole, the sediment grading appears to show little change at any stage of rainfall event.(6) As for the equivalent sediment concentration, it is found that the spatiotemporal characteristics of those concentraion process curve are significantly affected by both rainfall directions and intensity. Given the physical interpretation of sediment concentration, it has more advantages to be a reference point while extreme disaster occurs during rainfall event, comparing with the traditional referrence points(peak runoff, peak sediment discharge only).(7) Canonical Correlation Analysis (CCA) based on SPSS is showed to be valid of studying the rainfall-runoff-erosion mechanism, especially for the downstream-moving rainfall events. Results showed that the hydrological process can be divided into instantaneous and cumulative responses, for which the driving forces are rainfall intensity and total rainfall, and coupling with splash erosion and wash erosion, respectively. A relatively comprehensive interpretation of correlations between rainfall characteristics and hydrological response characteristics can be got from the CCA results.(8) Via experiments of static rainfall events under different locations above the slope, it is showed that different rainfall locations induce obvious influences on the correlations between peak sediment yield and peak runoff discharge, as well as the correlations between total sediment yield and rainfall intensity. Even more remarkable, rainfall locations also have significant impact on the characteristics of sediment concentration process curves, and the erosive sediment grading. |
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