基于约束性CA方法的北京城市形态情景分析

Form Scenario Analysis Using Constrained Cellular Automata

约束性元胞自动机(Constrained cellular automata,Constrained CA)在模拟城市增长方面已有诸多实践,已有文献常利用各种反映土地利用需要、区位影响、管理制度等的政策参数,设定不同的城市空间发展情景以反映未来的城市形态。在基于约束性CA进行城市形态情景分析时,以各种政策参数作为情景条件的研究实例较多。而在中国的城市规划实践中,城市规划用于建设管理的审批,对应明确的城市形态,因而如何利用城市形态作为情景条件分析所需政策,也有实践意义,可以解决一些广为关注的重要问题,例如已有的发展政策是否与期望的城市形态相匹配,不同规划方案所需采取的政策有什么区别等。本文提出了以城市形态作为情景条件(即形态情景分析)的新方法,该方法基于约束性CA,改变了传统的约束性CA情景条件的设置方法,以期望的未来城市形态为目标,识别相应需要的发展政策。并将北京市域的4个规划城市形态作为情景条件进行了实证分析,对多个规划方案实施的可能性和政策参数进行对比分析,证明该方法具有较好的适用性和可行性,是将约束性CA的应用扩展到城市规划领域的又一尝试。

Scenario analysis has been widely applied in the realm of urban and regional planning.In most of current scenario analysis researches of urban growth,developing policies are set as the input scenario conditions to generate various urban forms,which can be referenced by policy makers and urban planners.This paper reverses the line of current scenario analysis for urban growth,in which the term of form scenario analysis （FSA）,a spatial explicit approach,is novelly defined,employing the urban form as the scenario condition and aiming at identifying whether any policies set can be implemented to realize the predefined form.If yes,what the detailed policy implications are for the scenario form should be answered.A constrained cellular automata model （CA） is developed for FSA,which borrows the routine model calibration method of constrained CA using historical observed forms from existing literatures.Four planned schemes of Beijing Master Plan 2020 for the Beijing Metropolitan Area are analyzed using constrained CA to test FSA approach,and the corresponding required policy parameters are generated,together with policy implications for the study area.FSA is proved to be suitable for urban planning practice.