Bioswales

What are Bioswales?
Bioswales are vegetated, mulched, or xeriscaped channels that provide treatment and retention as they move stormwater from one place to another.  Vegetated swales slow, infiltrate, and filter stormwater flows.
As linear features, vegetated swales are particularly suitable along streets and parking lots.
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Designing a Bioswale
For best results, enhance and utilize existing natural drainage swales whenever possible. Existing swales can be enhanced with native plants. The thicker and heavier the grasses, the better the swale can filter out contaminants. Additionally, subgrade drains and amended soils may be needed to facilitate infiltration.

Other considerations when designing or maintaining bioswales:
• Costs vary greatly depending on size, plant material, and site considerations. Bioswales are generally less expensive when used in place of underground piping.
• Deep-rooted native plants are preferred for infiltration and reduced maintenance.
• Soil infiltration rates should be greater than one-half inch per hour.
• A parabolic or trapezoidal shape is recommended with side slopes no steeper than 3:1.
• Avoid soil compaction during installation.
• Swales should be sized to convey at least a 10-year storm (or about 4.3 inches in 24 hours).

Maintaining a Bioswale
Once established, bioswales require less maintenance than turf grass because they need less water and no fertilizer. Native grasses and forbs  are adapted to NY rainfall patterns. Natives also resist local pests and disease.