Dry and Wet Swales Flow Regulation and Overflow
Primarily on-line, but consider off-line when inflow is piped
Sized for WQV treatment, larger storms bypassed
Swales can receive runoff as concentrated or sheetflow
2-year non-erosive velocities
Adequate capacity for 10-year storm with 6” freeboard
Notes:
The dry and wet swales can receive runoff from concentrated sources (pipe outfalls), as well as from lateral sheet flow along the length of the practice. A diversion structure within the drainage network is the preferred method for diverting concentrated flows, prior to entering these treatment practices.
The overflow element of the dry and wet swales consists of safely conveying the high flow events (storms greater than the WQv) through the systems. This involves ensuring that the velocities of more frequent high flow events (e.g., 2 year storm) are non-erosive, and that the less frequent high flow events (e.g., 10 year, or in some cases, the 100 year storm) are contained within the channel, and do not pose a flooding condition to adjacent areas.