| The flood disaster is the highest frequency of occurrence in China,which caused the most serious losses among all kinds of natural disasters.Changes of the characteristics of landscape pattern caused by human activities result in the variation of the hydrological factors and it has rised the flood disaster level both in frequency and harm degree.Landscape pattern evolution mainly expressed as landscape patch type,size,shape and spatial configuration changes etc.,it changes cover interception,evaporation,the flow generate and aggregate mechanism and so on,which affecting the whole process of runoff.Studing the influence of the landscape pattern changes on different time scales of the peak flow systematically,can more fully reveal the changes of landscape pattern of flood The water response mechanism.Xixi watershed which is located at southeastern China and is one of the regions where the economy grow fast and the landscape pattern change dramatically was selected as a study area,carrying out research in these following aspects:(1)Setting up the HEC-HMS model in Xixi watershed,calibrating the sensitive parameters the initial abstraction ratio and the wave velocity and explore its' calibrate rule.(2)Exploring the influence of division of subbasins on HEC-HMS model simulation results of the internal watersheds based on the connection in space,and try to find out the proper mumber of sub-watershed to build flood model.(3)The annual largest flood under the meteorological conditions from 1996 to 2010 was simulated with the landscape maps in two periods of 1985 and 2006 using the Hydrologic Modeling System(HEC-HMS),respectively.Five kinds of time scale such as maximum 1 hour and maximum 6 hours were chosen to statistics the flood peak flow.Pearson correlation analysis method was also used to analyze the effects quantitatively.Results showed that:(1)The values of initial abstraction ratio and flood wave velocity were properly determinated and the accuracy of the model is high with the application of Approximate Circulating method in the calibration of the model;(2)The establishment of two empirical relationship between the initial abstraction ratio and the initial discharge,flood wave velocity and maximum rainfall intensity of 1 hour,is helpful for the model's application in flood forcast;(3)The watershed subdivision affect the simulated results of the outlet slightly but strongly in the subbasins;(4)The change of flood peak flow was significant correlated with the area change of landscape types such as forest,water area,urbanized area as well as the change of landscape indexes such as LPI,LSI,Division,SHDI,SHEI and AI;(5)The correlation between the change rates of flood peak flow and the change of landscape types and landscape pattern indexes increased with the decreasing of time scales indicated that the time scale of 1h was more reasonable to describe the response characteristics of flood process to the landscape pattern changes in the watershed. |
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