Abstract:Compared with the environmental risk assessment (ERA) for single project, regional ERA is usually featured with limitations, such as information shortage, more risk factors and increased difficulty in synthesizing multiple risks arising from diversified sources. Among the existing methods for ERA, the information diffusion approach (IDA) is capable of addressing the problem of information shortage and fulfilling a synthesis of multiple risks at regional level by building up and running risk information matrices. The risk zoning map, as an output of ERA for regional planning, shall be used for guiding layout planning optimization and risk management. In this paper, IDA was applied in an ERA for regional development planning of the Nansha area of Guangzhou. A four-level classification was made for the synthesized environmental risks brought about by the existing and anticipated risk sources within the area. The result indicates that the planned petrochemical base might increase environmental risk level of the area to a large extent. Thus, it is recommended that the petrochemical base should be either removed out of the planning or relocated to a more environmentally suitable site. This recommendation has been accepted in the final planning of the Nansha area. In order to achieve environmental optimization of regional development and enhance regional environmental risk control, this paper suggests an early incorporation of ERA into the planning process by examining environmental rationality of regional function distribution and industrial layout.