选择大清河水系的紫荆关流域为研究区,分析了其下垫面变化趋势,根据大清河水系的水文气象特点,建立了考虑下垫面变化的超渗-蓄满耦合产汇流模型,并利用实测暴雨洪水资料进行了参数率定和模型验证。利用该模型研究了流域洪水对下垫面变化的响应。结果表明:下垫面变化导致洪峰和洪量变小,其对大洪水影响小,对中小洪水影响较大。对于10年一遇以上洪水,由于下垫面的变化,洪峰和洪量平均分别减少1.3%和4.9%,小于5年一遇洪水洪峰和洪量分别减少5.8%和12.5%。通过不同下垫面因素变化条件下的模拟,认为土地利用类型之间的相互转变对洪水的影响较小,而土壤蓄水容量的增加是引起洪水明显减小的主要原因。
Flood peaks and volumes have decreased in Daqinghe River Basin in recent years. To search for the effects of underlying surface on flood decrease, Zijingguan watershed in Daqinghe River Basin was selected as a study area, and the statistical analysis of the underlying surface change was done, including land use change and soil moisture storage capacity variation. The remote sensing land use data of 1980 and 2000 were used, and the main change is forest increase, but grassland and arable land decrease. We selected several large floods to evaluate soil moisture storage capacity, and it is 110 mm before 1980, whereas 120 mm after 1980. A hydrological model was established considering underlying surface according to the hydrologic characteristics in Daqinghe Basin, in order to quantify the effects of underlying surface on floods. This model considers different types of land use, and the runoff generation was calculated for each land use type. The infiltration excess and saturation excess runoff generation mechanism was used. Finally, it was calibrated and verified by the historical hydrological data, and the Nash coefficients are about 0.70. It means that this model is consistent with the fact, and it can be used to analyze flood response to underlying surface change in the Zijingguan watershed. We simulated several floods under scenarios of 1980 and 2000, respectively. The results showed that both flood peak and volume decreased as a result of underlying surface change, and the effects are small to large floods, about 5% decrease for 10 years return period. It is shown that transfer of land use types has minor effect on floods, and the increase of soil moisture storage capacity is the main cause of decrease of flood peaks and volumes.
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