Tribute to Plants: Urban “Infrastructure” to Manage Stormwater

Now that spring’s here and the sun is shining, trees are budding left and right to bring a bit more color to our daily lives. This week- if not every week- I encourage you to stop, “smell the flowers”, and give a little praise to our vegetative friends.

To pay tribute to the awesome plants in our lives, I’ll be writing a series of informative blog posts in the next few weeks to highlight the role that vegetation can play in solving some common environmental problems. Today: green infrastructure.

The Issue: Stormwater Runoff

When rain hits impervious and compacted areas (e.g., rooftops, roads, driveways, walkways, parking lots), a much greater amount of stormwater is created when compared to the same storm falling over a forested area.

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Water in urban areas flows into storm drains and local streams, lakes, wetlands, and rivers which can cause flooding, erosion, depletion of groundwater, loss of habitat for out fellow critters, and pollution.

As stormwater runoff flows, it collects fertilizer (e.g., nitrogen and phosphorous), pesticides, sediment, motor oil and grease, litter, etc. that pollute waterways and can contaminate drinking water. Check out this website for some good tips and tricks to limit your potential negative impact on water quality.

In the United States, the Clean Water Act gives the  Environmental Protection Agency (EPA) authority to regulate stormwater. The EPA regulates point source pollution, from sources including industrial stormwater discharges and municipal separate storm sewer systems (MS4), through issuance of National Pollution Discharge Elimination System (NPDES) permits.

Non-point source (NPS) pollution, such as agricultural and typical stormwater runoff, is not included in EPA’s regulations, although the EPA awards grants for research and development to increase NPS mitigation and control. NPS mitigation and control focuses mainly on restoration and watershed protection, but also includes increasing green infrastructure in urban environments.

Many state and local governments have their own stormwater management laws, some of which include expanding their green infrastructure.

What is Green Infrastructure?

Using vegetation and soils, green infrastructure restore some of the natural processes required to reduce stormwater runoff and pollution and create healthier urban environments. And of course, adding greenery to any environment helps create oxygen, sequester carbon, and creates a habitat for wildlife.

There have also been many studies that show nature, including urban greenery, improves mental health and well being. (As if we need science to tell us what we already know-  don’t you feel better when you’re outside amidst nature? Go green!)

There are many types of green infrastructure: rainwater harvesting, rain gardens and bioretention areas, bioswales, permeable/porous pavements, green roofs, detention tanks, and stream buffer restoration, to name a few.

Rain Gardens, Bioretention Areas, and Bioswales

Rain gardens and bioretention areas (larger rain gardens) encourage stormwater to seep into the ground rather than flow into storm drains and surface waters. They are sited near impervious areas in depressions and holes so water can instead flow into the garden and percolate into the soil to reduce the amount of stormwater discharge. If constructed properly, rain gardens can soak up roughly 30% more water than a conventional patch of grass can.

Bioswales, typically located around parking lots and lining streets, are vegetated channels used to transport water, reduce discharge, provide stormwater infiltration, and give a little life to a concrete or asphalt slab. They replace the need for underground storm sewers and concrete open channels, which cost a lot more money for municipalities to construct. Plant some plants, and you’re good to go!

Rain gardens and bioswales act as natural filters, ridding stormwater of chemical and nutrient pollutants such as copper, lead, zinc, and nitrogen. (Full disclosure- phosphorous is a problem; more tends to leave rain gardens than gets absorbed.)

Bioretention Gardens in Vacant Properties in Detroit, Case Study

In collaboration with several Detroit, Michigan organizations, the University of Michigan Water Center research team recently created four beautiful bioretention gardens of flowering shrubs and perennials. These rain gardens were created on cost-effective  vacant property sites (i.e., demolished abandoned homes) in a Detroit neighborhood.

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Newly constructed bioretention garden in Detroit. Photo: University of Michigan.

Not only is this project making use of vacant space in Detroit, these gardens will improve water quality in the Detroit River and the Great Lakes and enhance neighborhood quality of life. (Let’s give Michigan a little bit of credit here, not every MI city is like Flint!)

During heavy storms, untreated sanitary and storm sewage escape Detroit’s sewage treatment facilities due to the large volume of incoming water. The combined sewer overflows (CSOs) flow into the Rouge River, which flows into the Detroit River and Great Lakes.

“The four bioretention gardens are expected to achieve an average annual storm water volume reduction of 1.2 million gallons.” This will allow the sewage treatment facilities to process more of the incoming water.

The Erb Family Foundation awarded the UM Water Center a $1.15 million grant to expand the scope of their work to include more green infrastructure projects throughout Detroit. Using these funds, the UM Water Center will work with the City of Detroit and a few local NGOs to assess the performance of the bioretention gardens over time and to develop new green infrastructure design concepts for Detroit.

The Detroit community is one of many cities and municipalities investing in green infrastructure to fix water quantity and quality problems resulting from polluted stormwater discharge. For example, the New York City’s Green Infrastructure Plan includes plans to increase rain gardens and green roofs throughout the city through a Green Roof Tax Abatement that incentivizes businesses to install green infrastructure projects.

There are many examples of green infrastructure projects throughout the world. Additional projects in the US include:

If you’re interested in creating a rain garden in your neighborhood, check out UMASS’s fact sheet for instructions and a list of viable plants. Or just Google it. Rain gardens are awesome and there is a lot of information about ’em.

 

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