Chemical, Biological and Radiological Hazard Assessment: A New Model of a Plume in a Complex Urban Environment

There has been a growing interest in recent years in the modelling of hazards arising from the atmospheric dispersion of chemical, biological and radiological (CBR) agents in the environment, and the threat that they pose to the population and military forces. This is a particularly challenging problem in an urban setting. Dispersion of CBR agents in an atmospheric boundary layer (ABL) over a heterogeneous (urban) canopy is a complex process to be described by advanced methods of fluid dynamics, turbulence theory, diffusion and statistics. Using comprehensive modelling is computationally intensive and too time consuming when applied to operational problems when reliable outcome has to be produced within a limited time frame. Plume characterisation requires the development of simplified analytical models of turbulent dispersion based on physical assumptions and “first principles” physics considerations. These models must still be simple enough to be easily treated numerically in an operationally viable way. Such models can also provide a theoretical foundation for “backtracking” problems, i.e. finding a CBR source in a complex canopy under various meteorological conditions. The purpose of this paper is to summarise the recent research conducted by DSTO (HPPD) in the development of such models.