基于SLEUTH模型的内罗毕城市扩张预测分析

Urban expansion and forecast analysis of Nairobi based on SLEUTH model

以肯尼亚内罗毕市为研究区,使用校准后的SLEUTH模型有效地对内罗毕的城市时空增长格局进行了监测、模拟并分析了内罗毕增长动力和方向,模型最终拟合得到参数分别为生长系数1、繁衍系数1、蔓延系数76、坡度阻抗75、道路引力69,3个校准步骤的拟合优度在0.5以上,符合精度的要求.SLEUTH城市扩张模拟显示2020—2035年内罗毕将会经历一个较快的城市扩张阶段,年均增速高于5%,2035—2050年城市扩张速率减弱直至趋于稳定,预测至2050年城市面积占县域总面积的60%左右.从空间上看,内罗毕未来的扩张方向为西北和东南方向.从影响扩张的因素上看,内罗毕的扩张与交通设施的建设、地形和原始土地利用分布密切相关,其中道路引力为主要影响因素.扩张区域主要集中在一级公路、火车站周围和坡度平坦的地区,其中耕地和草地通过土地利用转化,用作城市建设用地的比重最大.

In this paper,Nairobi,Kenya is used as the research area.The calibrated SLEUTH model is used to effectively monitor,simulate and analyze the growth momentum and direction of Nairobi’s urban spatiotemporal growth pattern.The parameters obtained by the model are:growth coefficient is 1;reproduction coefficient,1;spreading coefficient,76;slope impedance,75;and road gravitation,69.Meanwhile,the goodness-of-fit of the three calibration steps is above 0.5,which meets the requirements of accuracy.The SLEUTH urban expansion simulation shows that Nairobi will experience a fast urban expansion phase from 2 020 to 2 035,with an average annual growth rate of over 5%;and that the urban expansion rate will decrease between 2 035 and 2 050 until it stabilizes.It is predicted that by 2 050,the urban area will have occupied about 60% of the total county area.From a spatial perspective,Nairobi’s future expansion will extend in its northwest and southeast.Judging from the factors affecting the expansion,Nairobi’s expansion is closely related to the construction of transportation facilities,topography and the distribution of original land use.Among the three influencing factors,road gravity is the greatest.Expansion areas are mainly concentrated around first-grade highways and railway stations,and in areas with flat slopes.Cultivated land and grassland acquired through land use will take up the largest proportion of land to be used in the city’s future expansion.