Flood Response To Landuse And Landcover Change Of Wushui Basin

The Wushui Basin is located in Jingtoujiang County,Hengyang County,Hunan Province.Mountain floods often occur in the basin and the economic losses are relatively large.This paper selects the area above Jingtoujiang hydrological control station in Wushui Basin as the research basin,supervises the land use data in the study area by using the supervised classification method,and analyzes the land use transfer during this period;establishes the study watershed hydrological model(HEC-HMS)),and use the three parameters of flood peak relative error,peak current difference,and Nash-Suttcliffe efficiency coefficient to comprehensively evaluate the model's simulation results.Assuming extreme land use/coverage scenarios,the effects of land use types on flood factors were further studied.The main research contents and conclusions are as follows:(1)Based on the ENVI5.0 supervised classification,the land use data of the study area were interpreted in 1992,2000 and 2011.Based on the interpretation results,a land use transfer matrix was generated in conjunction with GIS.The land use in the three periods was analyzed.The cover is changed.The type of land use in the basin is mainly woodland and cultivated land.From 1992 to 2000,the research area was mainly converted from arable land to forest land and construction land.The size of the relocated area was arable land>forest land>bare land>construction land>water area,and the conversion intensity.The greatest is the conversion of arable land into forest land.The type of land use changed little from 2000 to 2011,and the forest land increased 2.39km2 as a whole.(2)Based on the results of remote sensing interpretation and GIS technology to extract information on the terrain,land use and land cover of the basin surface,using the HEC-HMS rainfall-runoff model,the SCS runoff curve method was used to calculate the production flow,using SCS units.The line method was used to calculate direct runoff,using the Muskingum method to conduct river course evolution,and using the exponential backwater model to simulate the base flow of the basin.The 20 floods in the basin were simulated and forecasted using the flood peak flow and peak present time.The results show that the model has good adaptability in the storm flood simulation of the Wushui Basin,and the simulation results of the single peak flood are better than those of the peak flood.Without changing other parameters,simulations were performed with time steps of 15 min and 60 min.The results show that the time step has a certain influence on the simulation results.As the simulation time step decreases,the peak flow rate increases,peaks The current time is irregular,and the simulation efficiency of most storm floods is improved.(3)Using the well-established HEC-HMS model,three typical flood processes were selected to analyze the effects of land use/cover change on the storm flood process from 1992-2000-2011.The results show that compared with the land use/coverage scenarios in 1992,the peak flood discharges have decreased in the simulation results under the 2000 scenario,with 3 typical storm floods(floods for 050610,floods for 080903,floods for 120610).Peak flow decreased by 10.3m3/s,4.4m3/s,and 20.92m3/s,respectively,with a decrease of 7.89%,10.04%,and 3.89%;the simulated flood peak in the 2011 scenario The reduction in flow rate increased,and the peak flow of three typical storm floods decreased by13.1 m3/s,5.7m3/s,and 29.22m3/s,respectively.The reductions were 10.04%and13.01%,respectively.5.44%.The change in peak time is not obvious.For the whole basin,the streamflow in the river basin is reduced,and the peak discharge is reduced.In addition,the production flow in different sub-basins increases and decreases.The increase in production flow is mainly concentrated in the middle and upper reaches of the south of the basin.(4)Assume extreme land use scenarios,simulate storm flood processes under different scenarios,and analyze the impact of different land use types on different storm floods.The results show that for the same flood,the increase of construction land has a significant impact on the storm flood process,not only makes the peak flow greatly increase,the peak time is ahead,but also changes the peak shape,forming a"thin" and "point" peak;Forestland helps to calm the peaks of floods and ease the storm floods in the basin.For storm floods of different magnitudes,the effects of land use types on small floods are more significant than those on floods.