上海中心城区土地利用变化对区域降雨径流的影响研究

Impact of 60 Years Land Use Change on Rainfall-Runoff in Central Shanghai

土地利用变化导致的城市下垫面改变对降雨径流关系有着重要影响。选择高度城市化的上海中心城区,利用初损和径流量修正方法并经实测数据验证后的SCS-CN修正模型,在城市集水区尺度上,初步探讨模拟了1947—2006年中心城区在0.5～10 a一遇设计暴雨重现期条件下持续1 h的降雨事件和丰、平、枯降雨年份下的径流系数,并分析了土地利用方式、前期土壤湿润程度(AMC)和降雨因素对中心城区60 a降雨径流关系的影响。结果表明:①60 a间,AMCⅠ和0.5～10 a一遇设计暴雨重现期条件下的径流系数相对增长17.21%～6.14%,枯、平和丰水年的年径流系数相对增长分别为20.49%、11.83%和10.02%;②土地利用类型、土壤入渗能力和AMC类型,与降雨强度共同构成影响降雨径流关系的两方面重要因素。随着降雨强度的增大,在AMCⅠ→Ⅲ过程中,土地利用改变对降雨径流关系的影响趋小,降雨类型起决定作用;而降雨强度越小,土壤AMC越干燥,土地利用改变对降雨径流关系影响越强;③不同降雨强度和降水年条件下的径流系数均随CN值的增大而增加,其径流系数与CN值之间分别可用线性(R2>0.999)和指数(R2>0.987)关系表示。

Underlying surface change caused by land use change had important influence on urban rainfall-runoff process. Based on actual measured rainfall-runoff data, the Soil Conservation Service curve number （SCS-CN） model modified according to initial abstraction and runoff was used to preliminary simulate the rainfall event runoff coefficients at 0.5 to 10 year rainfall recur- rence interval, and annual runoff coefficients at wet, normal and dry year condition in central Shanghai from 1947 to 2006. The impact factors of land use type, antecedent moisture condition （AMC） and rainfall on the rainfall-runoff relationship were analyzed. The results exhibited that ： 1 ） The CN value changing process could be driven into slowing increased period （1947 to 1984） , rapid increased period （1984 to 1993）, rapid decreased period （1993 to 2000） and slowing decreased period （2000 to 2006）. The major impact factors in the four periods were the change of cultivated land, cultivated land, water area and industrial land, respectively. 2） The rainfall event runoff coefficients of 0.5 to 10 year rainfall recurrence interval rainfall, at AMC Ⅰ , increased relatively from 17.21% to 6.14% from 1947 to 2006. Also the annual runoff coefficients at wet, normal and dry year condition increased relatively by 20.49% , 11.83% and 10.02% , respectively. 3） Land use type, soil infiltration ability and AMC, and rainfall were the two important influencing factors to the rainfall-runoff relationship. The impact of land use change decreased with the increase of rainfall intensity while AMC from I to m, and the impact of land use change increased with the decrease of rainfall intensity while AMC from Ⅲ to Ⅰ . 4 ） The runoff coefficient increased the with increased CN value at different event rainfall intensities and different annual rainfall conditions. The linear relationship and exponential relationship exist between rainfall e- vent runoff coefficient and CN value, and between annual runoff coefficient and CN value, with R^2 〉 0. 999 and R^2 〉 0. 987, respectively.