bioswale

This is road verge taken deep to filter many road pollutants out of rain runoff.

Bioswale concept diagram:

1. Dirty and polluted water from rooftops, roads and parking lots enters the bioswale
2. Water is slowed down by various plants and rocks, pollutants settle out, clean water infiltrates the soil
3. Water enters the perforated pipe and is slowly absorbed into the ground
4. Excess stormwater exits the bioswale and flows through the pipe into the recipient, cleaner then when it entered and in the amount significantly reduced.

source: https://www.researchgate.net/figure/Bioswale-concept-diagram-1-Dirty-and-polluted-water-from-rooftops-roads-and-parking_fig1_335219312

In Brooklyn, an abundance of street-beautifying bioswales means healthier, less polluted waterways. (Photo: NYC Water/flickr)

source: https://www.mnn.com/earth-matters/climate-weather/blogs/meet-the-bioswale-new-yorks-new-weapon-in-the-war-against-water