Dry swales, often known as “running bioretention”, are a great way to reduce runoff and maximize pollutant removal within the existing stormwater conveyance system. They can usually be applied in any open channel or road right of way (if it lacks curb and gutters). The basic design of dry swales was first introduced in 1996 in Design of Stormwater Filtering Systems. We have learned a lot more about dry swales as communities have gained more experience with this practice across the Bay watershed, and a new Bay-wide design specification was released in the summer of 2009 to reflect this hard-won knowledge.
The main improvements involve guidance on checkdam and inlet construction, more info hydraulic conveyance, and more specific data on their construction sequence, facility acceptance and maintenance triggers. Please pass on your design suggestions to CSN on how we can further improve this important LID practice.