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

Basin climate environment, runoff generation and flow routing conditions have a decisive impact on the formation of the flood. In recent decades of Haihe River Basin, precipitation and rainfall intensity which are the two main factors of climate environment affecting flood have little change, but flood volume and peak discharge which are the two principal eigenvalue describing the flood size have great changes, indicating that the runoff generation and flow routing conditions of Haihe River Basin has changed and land-use change is one of the conditions . In this paper, to study the Daqing River basin, using statistical analysis and modeling methods to research the effects on floods under the changes of land-use. The achievements are as below.(1)Using linear moving average method, to study the changing trend of the precipitation,flood volume, peak discharge and runoff coefficient corresponding to the typical flood process during 1956 to 2000, the results present that the precipitation, flood volume, peak discharge and runoff coefficient of Fuping and Zijingguan basin were showing a decreasing trend, of which the decreasing trend of precipitation in Fuping basin is not obvious, while the flood volume and peak discharge shows a clear trend of diminishing year by year.(2)With the statistical analysis of the land-use change on Zijinguan, Fuping, Manshuihe, Chengtouhui and Zhangfang basin, results showed that of these five watersheds, grassland, forests and farmland types have relatively large proportion, while construction land and water area have small proportion. In the five watersheds, land-use change generally shows a reduction of grassland and farm land area, increase in forest area, and the trend of grassland and farm land changing towards forests.(3)Using correlation analysis and partial correlation analysis, conduct a statistical analysis of the correlation among various land-use types and flood volume and peak flow modulus, the results show that the rate of grass cover, forest cover, the proportion of farm land ,flood volume modulus and peak flow modulus all show no significant correlation, of which the correlation coefficient among forest cover rate, the flood volume modulus and peak flow modulus is greater than the grass cover rate and the farm land cover rate, indicating the forest cover rate change has great influence on flood volume and peak discharge.(4)Using the runoff model based on land-use change, study the flood volume and peak discharge change caused by the transfer from one type of land-use to the other one under the condition that other land use types stay the same, the results show that the conversion among farm land, forest and grassland have little impact on flood volume and peak discharge, however, when the three types of land use transfer to the construction land, they have large impact on flood volume and peak discharge .