Study On Effects Of Land-use And Land-cover Change On Flood In Daqinghe River Basin

Land-use and Land-cover Change (LUCC) is a core field of the global change. As one of the environmental effects of LUCC, how flood responds to LUCC becomes the key point in hydrology.Haihe river basin, which is a typical region of semi-arid and semi-humid area in China, is one of the most serious region lack of water resources in China. In this context, to explore how flood responds to LUCC is of great theoretical and practical significance. Daqinghe river basin is selected as the study area. This paper developes a runoff yield and convergence model coupling of infiltration-excess and saturation-excess processes, considering land use and land cover change, and the model is verified in the study area. Historical inverse method is used to analyze the change of flood processes in different years The main contents and results are as follows:(1) The Haihe river Landuse data of 1980 and 2004 are used in this paper to analyze the LUCC trend of the study area by making use of spatial analysis function of GIS. The results show that the LUCC of Zijingguan basin and Fuping basin had put up a decrease of forest land and an increase of grassland, landuse of agriculture and urban.(2) Annual typical flood processes of the study area are statistically analyzed. Through comparision of the flood characteristics before and after 1980, the relationship between rainfall and runoff volume, the trend in storm runoff coefficients, flood resistance time and peak flow, the paper manages to analyze qualitatively the LUCC impacts on flood in Daqinghe river basin.(3) In order to evaluate quantitatively the flood effects of land-use and land-cover change (LUCC), a lumped watershed hydrological model considering land use and land cover change (LWHM-LUCC) is developed. In LWHM-LUCC, based on the first-order type of land resources classification system of Chinese Academy of Science, a basin is divided into five different types of LUCC. On the area of each type of LUCC, considering the difference of evaporation and infiltration respectively, the runoff is calculated by using runoff yield model coupling of infiltration-excess and saturation-excess runoff. The runoff discharge of each area is routed to the outlet section of basin by using unit hydrograph and linear reservoir model, thus the basin hydrology discharge processes are obtained. After parameter calibration and model validation, the model provided relatively good fits between simulated and observed flow. It is an advantaged approach to analyze flood response to LUCC by using the model.(4) The historical inverse method is adopted by hydrological model that is validated. The flood processes after 1990 were simulated Based on land surface parameters of 1980; and flood processes before 1980 were simulated based on land surface parameters of 2004. It is used to analyze the impacts of different land use and land cover on flood with the same rainfall process, especially to study the changes of LUCC impacts on peak flow and flood volume.