Trees, Rain Gardens and Barrels

Stormwater Runoff – How to Reduce Its Impact


Small streams in Nashville are characterized by a series of problems, found in most city streams, called urban stream syndrome.  The syndrome includes:
Quick rises in stream water levels during storms and more frequent flooding.  This is also called a flashy hydrograph.

  • Elevated levels of nutrients and contaminants.
  • Altered channel morphology which means that the bank is eroding and/or depositing sediment more rapidly than expected.
  • Reduced biotic richness – not a lot of biological diversity is found in the stream.  The species that still live in the urban stream are pollution tolerant and begin to dominate the stream ecosystem, think of it as the stream equivalent of squirrels and pigeons.

Most of these impacts are linked to storm water run-off. That is, the water that flows down into catch basins in your neighborhood when it rains. That water flows into the nearest stream…rapidly and full of pollutants from the roof, yard and street. To solve the problem of storm water runoff we need to restore as much of the preexisting hydrologic system as possible. In other words, we need to increase the infiltration of rainwater into the ground. No, we don’t need to raze our cities. But we do need to give the rainwater a place to sink into after it falls. Technically, this is considered reducing our effective impervious cover.

The really great news is that we can help our small streams all the while making our yards more beautiful, saving money, saving energy and providing our gardens with healthier water. Maybe your grandparents used cisterns, if so you’ll be familiar with many of the ideas below that will improve our small streams. It is easy to get started.  We have descriptions, links and photos below. Plus, we have frequent workshops for hands on learning.

Goals and Progress to Date
The Cumberland River Compact and Metro Water are working together to oversee the planting of 10,000 trees and build 300 rain gardens.  This joint project will reduce storm water run off and improve water quality.  Most importantly, the citizens of Nashville will become stewards of their waterways.  Each tree and rain garden will be recorded and mapped.  If you’d like to help Nashville reach its goal, please contact  Follow the hyperlink, if you’d like to register your tree or rain garden.

Rain Barrels
Rain Barrels are used to harvest rain from the roof top.  We recommend that the harvested water be used for outdoor purposes only.  You might be surprised by the amount of water you collect:  one inch of rain on 1,000 square feet of rooftop creates over 600 gallons of water.
Using a rain barrel can save you some money, give your plants a water they will like more than tap water, and help to slow storm water runoff.  You can also save energy used when the water is processed to drinking standards.  It is crazy when you think about it – we use drinking quality water in our yards and toilets.  Locations where water is scarcer already use gray water when drinking quality water is not necessary.

You can purchase rain barrels from the Cumberland River Compact and Metro Water.  More information is available on their websites.

You can also make your own rain barrel.
List of Supplies and Building instructions for Rain Barrels:


  • 55 gallon barrel- $6.00 from a soda bottling company
  • 1/2” Hose Bib spigot - $7.93 from Home Depot
  • Hose adapter ¾”mh x ½” mip (Watts stock # A-663)
  • Mesh Screen
  • Drill with spade bit ¾”
  • Reciprocating saw

- saw opening in barrel. 
- drill opening for overflow valve (hose adapter)
- twist in hose adapter, do it a few times – try to get it flush with barrel
- drill hole for spigot
- twist in spigot, do it a few times – try to get it flush with barrel
- cut piece of mesh to cover opening on top
- attach mesh to top of barrel with a bungee

To install place barrel under downspout. Take a hack saw and cut gutter 12” above top of rain barrel. Attach an adapter either elbow shaped metal gutter piece or plastic articulated piece to direct water into barrel. 

Tips:  When the barrel is full direct water away from your house with a long plastic pipe available at home improvement stores.  Also, drop a mosquito dunk in the barrel during the summer months to lessen mosquito problem. Elevating the barrel on a few cinder blocks will help water flow out of the barrel.


Rain Gardens


Great How-To Web Sites
The detailed directions at the sites linked below are similar and provide the evaluation, planning, and construction information needed to create a successful rain garden.

Guide written by local gardener, Patty Ghertner

Rain Gardens of West Michigan

Univ. of Wisconsin Extension, “How-To Manual for Homeowners” PDF download 

Virginia Department of Forestry

Rain Garden Design Templates (the piedmont region will be most similar to Middle Tennessee’s climate):

American River's Rain Gardens: The Mini-Series
In a series of short videos, American Rivers' rain garden expert, Gary Belan, provides tips on designing your backyard rain garden.  For more information, visit:


Why Native Plants?


Each of the rain garden Web sites above recommends the use of native plants.  There are several associated benefits.  Native plants are adapted to the local climate including seasonal variations in temperature and precipitation.  They are uniquely adapted to local soils, and many species develop deep roots for greater drought tolerance, requiring less water and care once established.  The shared geologic history of native flora and fauna established longstanding mutual relationships that also help gardeners.  Native plants provide the perfect habitat to attract and support local wildlife such as birds, butterflies, and other insects and animals that in turn provide pollination and natural pest control. 

Non-native or exotic plants, which do not have these adaptations, may find it difficult to survive or could become invasive, escape and damage natural areas.   Some well-behaved garden plants from other parts of the world, such as Japanese iris, or other parts of the U.S., such as Louisiana iris, may be good candidates for rain gardens.  Please be sure the plants you choose are not recognized in Tennessee as invasive by checking the Invasive Exotic Pest Plant list at  

Many native plants may be purchased from garden centers and retail nurseries in Tennessee.  There are several nurseries that specialize in natives, and some of them do mail orders.  Please make sure that the native plants you buy are nursery-propagated and not collected from the wild.  The following Tennessee nurseries are great sources:
GroWild Nursery, Fairview -
Nashville Natives, Fairview -
Moore & Moore Garden Center, Nashville -
Sunlight Gardens, Andersonville –
Native Gardens, Greenback –

Plant List 
The native plants linked in the pdf below can tolerate the varying degrees of wetness associated with rain gardens.  Most of them can also tolerate dryness.  Plants checked as ‘Dry’ also tolerate drought.  There are many, many more native plants available for moist to dry soils that may be planted on the periphery of a rain garden.   
Note:  Some plants may display aggressive behavior in the ample moisture of a rain garden.  Those marked with one asterisk (*) are known for their strong vegetative growth.  Those marked with two asterisks (**) are annuals that may self sow heavily.