Environmental Limitations to Vegetation Establishment and Growth in Vegetated Stormwater Biofilters
Over 100 bioswales have been constructed in King County over the past ten years to treat runoff associated with residential, commercial and light industrial development. Water level fluctuation, long-term inundation, erosive flow, excessive shade, poor soils, and improper installation are the most common causes of low vegetation survival in these swales. The relative importance of these limiting factors may vary widely from swale to swale. This study was designed to identify those factors that most influence vegetation establishment and growth, so that recommendations can be made to improve future biofiltration swale design and performance. The presumed relation between vegetation abundance and bioswale performance was also investigated. Environmental conditions were examined for eight biofiltration swales in King County, Washington, to determine the relative importance of the various factors influencing vegetation establishment and growth. Three of these swales were regraded, retrofitted with new soil, and hydroseeded in September 1996. A nested two-factorial greenhouse experiment tested the response of four turfgrass species, commonly seeded in bioswales, to four moisture regimes (three inundation schedules plus a control).
- The Water Center