Another way to slow water down after a rainstorm is to send it to a settling pond. The water gets to sit there slowly draining towards the creek or into the ground. If the water going into the pond is dirty, the pond lets the water slow down so that the dirt can settle down to the bottom of the pond instead of flowing to the creek. While the water is sitting, larger and heavier particles sink to the bottom of the pond so the nearby stream receives cleaner water.
Sustainable drainage features provide many benefits such as providing water quality treatment, reducing channel erosion, controlling flooding by reducing peak flow and flow volume, and recharging the groundwater.
- See more at: http://www.surrey.ca/city-services/3646.aspx#sthash.uHTwzrnr.dpuf