A bioswale is a multi-purpose stormwater management practice that provides an alternative to storm sewers. By using a permeable soil bed and perforated subdrain tile, bioswales infiltrate water from frequent, small rains (~1.25″ or less.) During heavy rains, bioswales convey runoff in a non-erosive manner. 

Above ground, bioswales can be subtle and feature typical turf grass, or be designed as an attractive flower garden with native plants and grasses. Whatever vegetation is used, it is important that it protects against soil erosion, the deeper the roots, the better. 

Bioswales are considered “green infrastructure” because they offer water quality benefits not provided by traditional storm sewers. This is a relatively new stormwater practice, but it has been very popular. 

Bioswales that utilize existing natural drainage swales often provide the best results. Bioswales can be installed where drainage swales are eroding, where low-lying areas can pond stagnant water, or in lieu of stormwater pipes. 

Plants: 
Vegetation should provide critical erosion protection and be aesthetically pleasing.

Berms:

Berms ensure water is slowed down and infiltrated, helping remove pollutants common to stormwater runoff. Berms can be constructed of earthen material or rocks.

Modified Soil:

Amended soils are placed into the bioswale to facilitate infiltration of water during rainfall and runoff events

Washed Rock:

The subdrain tile is bedded in clean, washed rock

Perforated Subdrain Tile:

Drainage tile ensures water can percolate down through the soil. If water can’t move down through the soil profile, it will move to the subdrain and be conveyed to a stream or other outlet site in an controlled manner.

Maintenance:

• the primary maintenance is managing vegetation to keep a pleasant-looking appearance
• perform weed control as needed
• if turf grass is used, maintain a height of no less than 4″ to filter and capture pollutants and protect against erosion. 
• If native vegetation is used, burn annually if local code allows.
• If burning is not feasible, mow and remove domant vegetation annually
• Inspect annually for bare soil or scour erosion.
• inspect annually for sediment accumulation. bioswales trap sediment that will periodically need to be removed
• remove accumulated trash and debris