Developing Multiple Lines of Evidence to Decrease Drainage-to-Surface Area Ratio for Effective Stormwater Control Sizing Using Bioretention.

Abstract

Defining the size of stormwater controls can be difficult because there are often multiple objectives imposed on the final design of these structures, including safety and flooding. Results presented here would indicate that if the objective is to create a bioretention area with healthy vegetation, undersized controls may be acceptable because undersized infiltrating controls will have healthier plantings and infiltrate throughout the storm. For municipalities, this means that rights of way previously thought to be too small to use for infiltrative stormwater controls may be converted to such a purpose. This does not free municipalities from stormwater systems that address flooding and safety design objectives, but demonstrates that increasing plantings in the municipal right of way could help to address stormwater as well as other objectives, like greenhouse gas emissions, urban heat island reduction, and clean air. Distributed bioretention controls that capture part or all the runoff of the smaller, most frequent rainfall events should be incorporated throughout municipalities and into their overall stormwater control systems. If clogging by runoff is a concern, roof runoff may be more appropriate for bioretention, or other measures such as sediment capture or increased maintenance may need to be performed.