Rock weirs (a pile of stones lined up to slow down the flow of water on a hill) and compost filter sock check dams are used in place of traditional sediment and erosion control such as silt fences and straw bales. They:
- are used to control and keep sediment from soil erosion from flowing downhill, as is the case in newly constructed rain gardens or bioswales where soil has been exposed.
- slow the velocity of the flow of water, either at the inlet to the rain garden, the overflow of a rain garden or on a slope, thus reducing the potential for erosion.
- when placed at intervals along a bioswale, they slow down the velocity of water flowing through a bioswale.
- when used on hard surfaces, they prevent sediment from flowing into other areas.
- aid infiltration of water into the soil by slowing water flow.
For more details on how and when to use filter sock check dams and weirs, see Stabilize Steep Slopes.