城镇化对金堂县城区洪水的影响分析

Influence of Urbanization on the Floods in Jintang County

随着城镇化进程加快,金堂县城区洪水问题越发突出,给当地经济社会可持续发展带来了巨大挑战.为了金堂县城区防洪安全和防洪规划需要,本研究以1980年城市化初期的土地利用为背景,通过构建分布式SWAT水文模型,以2018年的暴雨洪水为典型,探讨了1980年、2000年、2018年三种不同城镇化水平下金堂县城区洪水的变化情况.结果表明:(1)以沱江以沱江干流三皇庙水文站为控制的分布式SWAT水文模型能够较好地揭示金堂城区洪水的演变情况,模拟精度满足洪水预报要求,其中纳西效率系数(NSE)达0.91,确定系数R^(2)达0.82.(2)1980~2018年土地利用类型变化主要表现在耕地向建设用地的转换,耕地占比减小7.68%,建设用地占比增大了7.1%.(3)1980年、2000年和2018年三种土地利用情境下,假定金堂县遭遇2018年类似的暴雨,通过分布式SWAT水文模型的模拟分析,以三皇庙水文站为代表的2000年和2018年金堂县城区洪水的洪峰流量分别比1980年增加了0.13%、11.13%.该研究结果也进一步表明金堂县城区洪水跟沱江三皇庙水文站控制集雨面积内的城市建设用地迅速增加和农林用地的锐减密切相关,即城市用地增加1%,对城市洪水的贡献率(以洪峰计)达1.5倍以上.该研究成果可为金堂城区的防洪规划、防灾减灾等提供一定的参考,研究方法也可为类似的城市洪水研究提供一定借鉴.

With rapid progress of urbanization,flood problem in Jintang County is becoming more and more serious,which brings great challenges to the sustainable development of local economy and society.In order to meet the needs of flood safety and flood control planning in Jintang County,this study takes the land use in the early stage of urbanization in 1980 as the background,constructs a distributed SWAT hydrological model,and takes the rainstorm flood in 2018 as a typical example to investigate the changes of flood in Jintang County under three different urbanization conditions in 1980,2000,and 2018,respectively.The results of this study indicated that:(1)the distributed SWAT hydrological model constructed based on the Hydrological Station of Sanhuangmiao on the Tuojiang River could satisfactorily represent the evolution of flood in Jintang city,and the accuracy of simulation meets the requirements of flood forecasting,in which the Nash-Sutcliffe efficiency coefficient(NSE)reached 0.91 and the determination coefficient(R^(2))reached 0.82;(2)From 1980 to 2018,the change of land use types was mainly converted from cultivated land to construction land,with the proportion of cultivated land decreasing by 7.68% and the proportion of construction land increasing by 7.1%;(3)Under the three land use scenarios of 1980,2000,and 2018,assuming that Jintang County suffered a similar rainstorm in 2018,through the simulation by the SWAT model,the peak discharge of urban flood in 2000 and 2018 represented by the Sanhuangmiao Hydrological Station increased by 0.13% and 11.13% respectively compared with that in 1980.The results can further demonstrate that the urban flood in Jintang County is closely related to the rapid increase of urban construction land and the sharp decrease of agricultural and forestry land within the catchment controlled by the Sanhuangmiao Gauge Station of Tuojiang River,and that the urban land increased by 1%,the contribution rate(in flood peak)to urban flood was more than 1.5 times.The results can provide a certain reference for flood control planning,disaster prevention and mitigation of Jintang city,and the research methods can also provide a reference for similar urban flood researches.