|Definition:||A bioswale is a man-made wetland built to encourage the drainage of water, diverting it from the sewer and water treatment plants.|
|Rendered as:||Should be rendered similar to wetland, but with some mark that indicates that it's manufactured.|
A bioswale is a manufactured wetland that's most often built to collect surface runoff water from sidewalks and roads, diverting the water from a city's (typically at-capacity) sewer and stormwater systems. Plant species native to the region are used as are species that soak up water quickly. They are designed also to replenish the water table; their permeable nature prevents flooding, unlike an impervious grass area. More and more cities are building these to divert water from their at- or over-capacity sewer and stormwater systems. In many cities these are the same system (known as Combined Sewer Overflow, CSO). You could also say they are "trendy". Regardless of their reputation, though, they are supremely useful at creating beautifully landscaped places in urban areas that double as water filtration systems and reduce the load of the sewer system.
Cities are using bioswales to increase their sustainable/environmental/green reputations and as such are of interest to visiting professionals in these careers. By tagging them in OpenStreetMap it would be possible to compare the area each city is dedicating to building these features.
Portland, OR, and Seattle, WA, in the United States are well-known for their use of bioswales. Portland has installed them in the parkway (the area between the roadway and the footpath/sidewalk/pavement). Chicago has several bioswales, used near parking lots to clean and drain those surfaces.
The tag would be man_made=bioswale. A bioswale is most like a natural=wetland and wetland=marsh, but the main distinction is that a bioswale is manufactured by humans.
The operator tag could be applied as bioswales are installed and managed by some organization.
Many bioswales would be mapped as a node, because they're quite small, but they can be of any size.
I propose that the bioswale would be rendered like a wetland, but with a slight variation to indicate its man_made nature.
I don't know of any at this time.