Revised design criteria for stormwater facilities to meet pollution reduction and flow control requirements, also considering predicted climate effects

There is a need to revise existing design methods for stormwater pollutant treatment, flow transport and detention facilities. The aim is to increase the accuracy in predicting the performance compared with design only based upon areal and volumetric functions and to optimize design by considering more site-specific data, receiving water quality criteria and forecasted climate effects. During the latest years, flow proportional concentration data from in- and outlets from wet ponds and constructed wetlands, have been compiled. Furthermore, other kind of data from the specific facilities have been compiled, such as areas, volumes, proportion of vegetation, outlet design details and length:width ratio. The parameters are used to revise design methods and are implemented in the operative stormwater and recipient software model StormTac. Design criteria and parameters for calculating design flow and sizing required detention volume are also presented. The climate effects on some of the studied parameters, e.g. design flow and inlet concentration, are discussed. The paper presents the climate factor based upon the hypothesis that it is a function of the design rain duration and reoccurrence time.