StormwaterPA’s Editors had their ears open at the Villanova Urban Stormwater Partnership’s (VUSP) Green Infrastructure Open House last week.  Here are a few highlights from Dr. Robert Traver’s report on recent preliminary research findings:

• Plant roots seem to maintain openings in the soil during freeze/thaw events, allowing continued infiltration; use plants with deeper roots, as well as plants with high ET rates.
• Rain garden problems are often caused by poor construction.
• Use of geotextiles between the sand medium and native soil on the bottom of basins/rain gardens may impede infiltration.
• Use a 50/50 mix of native soil and sand for an infiltration medium.
• Rain gardens and basins function well with a sand layer depth of 2 ft, where most plant roots are found, for faster infiltration and less long term compaction.
• Infiltrate relatively clean water through a treatment train design; for small storms (less than 1 in), use a pre-treatment method such as a grass/stone strip or rain garden; for larger storms, use rock bed infiltration or detention storage.
• Perhaps size and depth of storage “bowl” for infiltration can be decreased in size, compensated by an enlarged root zone and sand medium.
• Temperature of water effects infiltration rate (slower in the winter).
• Perhaps both bowl and root zone storage calculations - not just bowl calculations -  can be used.
• To make BMP’s last longer, avoid eroding surfaces from inflow.
• Design for pre-treatment.
• Clean out pre-treatment areas.

Learn More about VUSP here>>

admin Research, Stormwater BMPs, green infrastructure detention basin, erosion and sediment control, geotextiles, green infrastructure, infiltration, native soil, pre-treatment, rain garden, root zone, runoff prevention, stormwater basin, treatment train

The number of native fish and aquatic insects, especially those that are pollution sensitive, declines in urban and suburban streams at low levels of development - levels often considered protective for stream communities, according to a new study by the U.S. Geological Survey.

When the area of driveways, parking lots, streets and other impervious cover reaches 10 percent of a watershed area, many types of pollution sensitive aquatic insects decline by as much as one third, compared to streams in undeveloped forested watersheds. We learned that there is no ’safezone,’ meaning that even minimal or early stages of development can negatively affect aquatic life in urban streams.

–Tom Cuffney, USGS biologist

As a watershed becomes developed, the amount of pavement, sidewalks and other types of urban land cover increases. During storms, water is rapidly transported over these urban surfaces to streams. The rapid rise and fall of stream flow and changes in temperature can be detrimental to fish and aquatic insects. Stormwater from urban development can also contain fertilizers and insecticides used along roads and on lawns, parks and golf courses.

Stream protection and management is a top priority of state and local officials, and these findings remind us of the unintended consequences that development can have on our aquatic resources. The information has been useful in helping us to predict and manage the future impacts of urban development on streams and reinforces the importance of having green infrastructure to control stormwater runoff and protect aquatic life.

–Tom Schueler, Chesapeake Stormwater Network

USGS studies examine the effects of urbanization on algae, aquatic insects, fish, habitat and chemistry in urban streams in nine metropolitan areas across the country: Boston, Mass.; Raleigh, N.C.; Atlanta, Ga.; Birmingham, Ala.; Milwaukee-Green Bay, Wis.; Denver, Colo.; Dallas-Fort Worth, Texas; Salt Lake City, Utah; and Portland, Ore.

These USGS studies also show that land cover prior to urbanization can affect how aquatic insects and fish respond to urbanization. For example, aquatic communities in urban streams in Denver, Dallas-Fort Worth and Milwaukee did not decline in response to urbanization because the aquatic communities were already degraded by previous agricultural land-use activities. In contrast, aquatic communities declined in response to urbanization in metropolitan areas where forested land was converted to urban land, areas such as Boston and Atlanta.

Comparisons among the nine areas show that not all urban streams respond exactly the same. This is mostly because stream quality and aquatic health reflect a complex combination of land and chemical use, land and storm-water management, population density and watershed development, and natural features, such as soils, hydrology, and climate.

These USGS studies represent an integrated approach to understanding urban streams that includes physical, chemical and biological characteristics associated with urbanization. This is critical for prioritizing strategies for stream protection and restoration and in evaluating the effectiveness of those strategies over time.

For more information, listen to USGS Corecast Episode 127.

The full report and extended video podcasts are available at the National Water Quality Assessment program urban studies website.

admin Research aquatic life, development, green infrastructure, Nonpoint source pollution, pavement, stormwater, stormwater best management practices, stormwater runoff, urban development, urban stream, water quality