| The grain for green project had greatly improved the ecological environment on the Loess Plateau.At the same time,it also made the contradiction between man and land more prominent.Gully land consolidation Project(GLCP)was an effective means to supplement the amount of cultivated land,promote the development of agricultural economy and improve people's living standard.In recent years,all kinds of disasters caused by rainstorms had caused different degrees of damage to the land consolidation projects of the gullies.This made the change of river basin water environment after the land consolidation of the gully become a common concern of scholars at home and abroad.In view of the current situation that the process of runoff production and confluence after land consolidation in the loess hilly and gully region should be further studied,the method of combining physical model and mathematical model was adopted.The change of the process of yield and confluence in the river basin after the land consolidation of the channel was analyzed and the parameters of the mathematical model applicable to the river basin for the land consolidation of the gully were explored.In addition,the critical proportion of gully land remediation works under different vegetation coverage and different rainfall conditions was further explored.The main conclusions were as follows:(1)The GLCP had a significant effect on the process of yield and confluence.With the increase of the proportion of land consolidation in the channel,the time of runoff generation and confluence was prolonged,and the flow velocity,runoff coefficient,peak discharge and average discharge of the channel all decreased.The effects of GLCP in different vegetation-covered basins were not identical.The physical model test showed that when the vegetation coverage was 0%,the influence of land consolidation on the time of runoff production and confluence was the greatest.For the flow velocity of the channel and the number of runoff curves,the vegetation coverage of the early stage that had the greatest impact on the land consolidation of the channel was 25% and 50%.(2)The GLCP had a significant effect on the yield and confluence parameters of the basin.CN decreased with the increase of regulation proportion under the same vegetation coverage.Compared with the unregulated basin,the CN decreased by 6.77 when the regulation ratio was 20%.With the increase of the proportion of channel land consolidation,the decreasing rate of runoff curve number firstly increased and then decreased.When the regulation ratio changed from 0.5% to 5%,the CN decreased at the highest rate.Under different vegetation coverage,the effect of GLCP on the CN was not exactly the same.The influence of GLCP on the underlying surface should be considered in the application of SCS model.The verification results showed that the parameters obtained from physical model tests could be applied in the mathematical model.(3)The most significant critical regulation proportion interval existed in the GLCP.When the regulation proportion does not reach the area,the influence of the channel land regulation project on the runoff process was small.The physical quantity changed obviously when the regulation proportion was within the area.When the regulation ratio exceeded the area,the water reduction effect of the project will not increase.The vegetation coverage had little effect on the critical regulation proportion.Rainfall return period had a significant effect on the critical remediation ratio.Under the condition of rainfall once in100 years,the range of the physical model test was 0.5%?10%,and the range of the mathematical model calculation was 4.60%?6.10%.Generally speaking,the results obtained by the two were consistent in law and similar in value. |
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