hydrographs. The sediment concentration was normally very high, and the mean value was 9.58 ± 10.90 g l-1. For example, the runoff process observed during event 000817 in Kunniushan watershed produced two runoff peaks. The sampling points were located at the minor runoff peak (1–7 sampling points) during the initial stage and the second major runoff peak (8–24 sampling points). The sediment concentration was high during the initial stage of the first runoff peak. However, as the flow rate increased and then gradually decreased, the sediment concentration appeared to decrease logarithmically, which is consistent with the situation observed for the ML-type rainfall events (Fig. 3b). Conversely, during the initial stage (8–9 sampling spots) of the second runoff peak, the sediment concentration was maintained at a low concentration that was similar to the concentration observed at the end of the first runoff peak. As the flow rate increased (10–14 sampling spots), the sediment concentra- tion increased rapidly, with the highest concentrations being observed at sample spots 10 and 11, after which it decreased logarithmically as the flow rate changed. The sediment hydrographs produced for these events were different from those produced in studies conducted by Hamlett et al. (1984, 1987) and Pathak et al. (2004), who drew similar conclusions regarding storms in which the peak sediment concentrations generally preceded or occurred simultaneously with the peak runoff rates.
Similar reasons may have contributed to the sediment concentrations during the first runoff peak in the ML-type rainfall events. The extension of the rainfall event and the formation of the second runoff peak indicate that the loose surface soil was washed away during the rainfall event. In addition, the previously compacted topsoil was destroyed and larger rills began to develop during the ML-type rainfall events. As a result, the sediment concentration increased gradually after being maintained at a low level, eventually reaching a new plateau. However, when the compaction and development of the rills was sufficient, the
hydrographs. The sediment concentration was normally very high, and the mean value was 9.58 ± 10.90 g l-1. For example, the runoff process observed during event 000817 in Kunniushan watershed produced two runoff peaks. The sampling points were located at the minor runoff peak (1–7 sampling points) during the initial stage and the second major runoff peak (8–24 sampling points). The sediment concentration was high during the initial stage of the first runoff peak. However, as the flow rate increased and then gradually decreased, the sediment concentration appeared to decrease logarithmically, which is consistent with the situation observed for the ML-type rainfall events (Fig. 3b). Conversely, during the initial stage (8–9 sampling spots) of the second runoff peak, the sediment concentration was maintained at a low concentration that was similar to the concentration observed at the end of the first runoff peak. As the flow rate increased (10–14 sampling spots), the sediment concentra- tion increased rapidly, with the highest concentrations being observed at sample spots 10 and 11, after which it decreased logarithmically as the flow rate changed. The sediment hydrographs produced for these events were different from those produced in studies conducted by Hamlett et al. (1984, 1987) and Pathak et al. (2004), who drew similar conclusions regarding storms in which the peak sediment concentrations generally preceded or occurred simultaneously with the peak runoff rates.Similar reasons may have contributed to the sediment concentrations during the first runoff peak in the ML-type rainfall events. The extension of the rainfall event and the formation of the second runoff peak indicate that the loose surface soil was washed away during the rainfall event. In addition, the previously compacted topsoil was destroyed and larger rills began to develop during the ML-type rainfall events. As a result, the sediment concentration increased gradually after being maintained at a low level, eventually reaching a new plateau. However, when the compaction and development of the rills was sufficient, the
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