Assignment: Report of System Dynamics Model of Urban Sustainable Development

Report of System Dynamics Model of Urban Sustainable Development

IntroductionSystem dynamics(SD) theory recently has become a theoretical approach of studying development issues (Esther Thelen and Linda. B. Smith,1994). The concentration of this theory is on the complex and nonlinear systems. This theory provides a path of understanding the giant systems from the mathematical and statistical ways. System dynamics can be used in most of the fields to supply trustable and visible models. In addition, with the help of these models, the researchers are able to provide policymakers with suggestions more accurately. Meantime, policymakers are able to make better decisions with these suggestions and models.

MethodologyThere are mainly six steps of building a system dynamics model.
Step1 Distinguishing the issue.
Step2 Determination of the research object and scope.
Step3 Build the Causal Loop Diagram(CLD) and the Flow Diagram(FD).
Step4 Establishing System dynamics formulas.
Step5 Simulation and calculation.
Step6 Functioning the best system behavior which are selected by comparison, assessment and policy analysis.

The system dynamics method is a quantitative method. Its accuracy mainly depends on three parts, including the accuracy of the data, the procedure of modelling and the clarity of relationships of variables.The urban sustainable development case
An urban sustainable development system is a complex system which consists of several subsystems. In this complex system, the authors determined there exist six main subsystems which are typical and necessary, including the population, science and education, resource, economy, environment, social development subsystems. After the analysis and assessment of the relationships among the six subsystems, the authors built the scheme of the urban sustainable development system as below,


The scheme determines the basic principle for the next stage research of the subsystems and the strategic decision-making. But the analysis and assessment of this scheme are qualitative and cater to the need of the local government. Although sometimes it is very difficult to use a quantitative method to ascertain the relationships among these development elements, the qualitative method will lead the research to the situation of inaccuracy. The relationship between the society development and the environment is unclear as which happened to the resource subsystem and the science and education subsystem.

Then there is a flow diagram(FD) which is a typical system dynamics method tool. In the flow diagram of the society development subsystem, SWC represents the supply-water-capability, RA represents the road-area, and GB represents the greenbelt. SWCG, RAG, GBG are the growth of SWC, RA, GB, respectively, as rate variables. MIR represents the urban management-investment-rate, as control variables. GBA is greenbelt-average, RAA is road-area-average, WDI represents doorsill-investment and WUSD represents water-use-strain-degree, as the auxiliary. Then the flow diagram successfully clarifies the relationships among the main variables.


The other five subsystems follow the same principle and clarify the relationships of the main variables in the subsystems, respectively.

























With the six subsystem mix schemes and the whole system scheme, it is possible to gain a clear view of the relationships inside and the influence elements of the target city’s development.
After the researchers work out the formulas, they simulate the SD model and calculate the data. The error between simulative data and historical data is in the permitted scope. Hence, the researchers believed the SD model is successful.
Technically, there should be a causal loop diagram(CLD) in the first place. Because the CLD gains the clarification of the relationships of the variables and reveals the limitation of a CLD which could not distinguish the differences among the various variables (Xue Liu, 2015). Therefore, researchers build the flow diagrams(FD) to explain the inner influence with the exceeded time.
But in this case, the author failed to give a CLD. I believe the missing of the CLD will definitely increase the inaccuracy of the SD model.

Advantages and disadvantages of the system dynamics modelWith no doubt, the system dynamics model is a useful tool with amount of advantages, such as its accuracy and directness. But disadvantages are also obvious. As a method and tool to a complex giant system, the system dynamics theory only provides a possibility for researchers to analyze the issues. There might be plenty of impeditive problems, such as inaccurate data, difficulty of establishing formulas, deficiency of measurements and interference of qualitative method. It still depends on the ability of the researchers themselves.

Conclusion
The urban sustainable development case shows the procedure of building the system dynamics model and simulating the data. The research finally concludes that economy development is the first priority, and the simulative development of economy shows the significant benefit result. Since all the other subsystem development are based on the economy development. The trend of policy shall be towards the economy development.

ReferenceThelen, E., & Smith, L. B. (1996). A dynamic systems approach to the development of cognition and action. MIT press.1996
Zhang, R., LIANG, B. S., Liu, B., & ZHANG, H. (2005). Study on System Dynamics Model of Urban Sustainable Development and Demonstration [J]. Journal of Henan Agricultural University, 2, 026.
Liu, X., Ma, S., Tian, J., Jia, N., & Li, G. (2015). A system dynamics approach to scenario analysis for urban passenger transport energy consumption and CO 2 emissions: A case study of Beijing. Energy Policy, 85, 253-270.