Why rain gardens fail

.
Rain gardens are supposed to put runoff back into the ground.

But they don't do their job if the runoff never gets into them, if they overflow before the water sinks in, or if their bottoms are impervious.  I'll address the first two issues here.

Many large rain gardens--for example, those taking runoff from parking areas--aren't graded properly.  The runoff never gets into them.  Obviously, no one is checking to see if they really work.  I'll give three examples from parking lots.

Metcalfe's Sentry

In this large lot, there are 3-4 long islands between rows of parking, which are supposed to receive runoff from the gutters through gaps in the curb. 

These gardens fail because the basins aren't much lower than the gutter.  No water flows in.

And, there is nothing to deflect the swift flow in the gutter towards the garden.

Madison Gas & Electric visitor's parking

At this lot, we have--at the center of the lot--a filtration chamber.  It was designed to filter the toxic stuff dripping from vehicles, before the runoff gets to nearby Lake Monona.  The filtration was a cooperative project by MG&E, DNR, and other agencies to see how efficient filtration could be.

The filters reside in an underground concrete bunker--the setup cost $50,000. It basically does the job a larger rain garden could do.

 

While this wasn't a rain garden, they did measure how effective the parking area was at gathering water and feeding it to the filters.  Since the parking area wasn't graded to be an effective catchment basin, it sent 30% of the water to surrounding streets.  Only 70% of the water falling on the pavement actually went to the filters.

The area within the red line drained to the filters. The area between the red and yellow lines drained to the street--wasted.

So a rain garden (or filtration system) is no more effective than the grading and inlets to the garden.  If the grading isn't carefully done, you've wasted a lot of money.

Terrace rain gardens on Eaton Ridge

These were among the first rain gardens on terraces, built by the City.

Rain garden inlets on Eaton Ridge were too small, and quickly became clogged.

 

Terrace gardens built by the City on Adams St had better entrances.

Sequoya Commons

This is a beautiful rain garden, with a large capacity.  For the most part, it is well-graded.  Nevertheless, a small portion of the north end of the parking area drains to the street, via the entrance to the lot.

 

My real purpose for mentioning Sequoya is that you can see this garden does reject some water.  I saw if overflow once in a heavy storm.

On another occasion, when the garden was full of water, a steady stream of clear water seeped from the garden into the storm sewer.  While this escaping water didn't get into the ground, at least it was clean and free from sediment.



The bottom line

Before you build a garden, always watch where the rain goes during a storm. 

Test the grade by pouring water on the pavement.

Don't pay the contractor till you see if the garden actually works.

If necessary, build a berm of earth or asphalt to correct the flow.

Rain gardens in New Zealand

.
New Zealand is an island country with keen environmental awareness.  Perhaps that's because they experienced some environmental disasters after colonization by Europeans.

Sheep and deer overran and denuded the country.  Erosion followed.  Species disappeared at an alarming rate.

So it's not surprising that their capital city--Aukland--has some interesting rain gardens.  Recently, I found the following photos on the internet.

The photos are mostly rain gardens for streets and sidewalks. If we're going to improve the lakes, we have to start dealing with street runoff in a big way! (Click on photos to enlarge.)

Rain gardens bring countries together

Rain garden, corner of Struck St. and Watts Rd.



Recently, I passed one of my favorite rain gardens on the way to Woodman's.   It's a large garden draining a parking lot, at the corner of Struck St. and Watts Rd.  I saw a group of people working on the garden, and decided to stop and find out about the garden.

City requests proposals for planting in existing rain gardens

.
On June 14, bids are due on a project to plant and maintain rain gardens in Madison.  Some of the gardens have already been constructed, while others are in the process of construction.  Glenn Clark is the project manager. Work will start about June 21 and end about Sept. 20. 

Existing gardens to be planted
Starkweather Creek rain garden
Marston Ave. rain gardens 1-5
Bernie's Beach bio-retention basin
Allied Drive bio-retention basin
Prairie planting at Beld St. and Wingra Dr.
Kipp rain garden
Westmorland Park rain garden
Vilas Park bike path
Vilas Beach

Newly constructed rain gardens to be planted
609 Gilmore St
2114 E. Mifflin St.
2106 E. Mifflin St.
Ivy Street rain gardens A and B
1000 Edgewood Ave.

The RFP calls for purchase of 4,896 plants, so you can see that "green infrastructure" is fast becoming part of our economy--a source of jobs.

#          #          #

See the RFP here.  There is a map of the garden locations on p.55, and species lists on p. 45.

From snowbank to sea

Reprinted from my "Save Our Stream" blog.

One warm day in March, years ago, my son Chris and I were walking in Forest Hills cemetery.   Everywhere, snow banks were melting into rivulets, coursing down the asphalt.

Chris asked: "Daddy--Where does the water go?"

As I explained about the water running into the sewer, then into the lake, then into the Mississippi River, suddenly a thought struck: "Why not actually show him where it goes?  Why not?" 

How to build a large rain garden on your terrace

.

Building this garden doesn't have to cost anything.  Once established, little maintenance is required.  The basic idea is to dig out the terrace, to below the sidewalk level.

How to build a small rain garden on your terrace

.

How to create an easy rain garden on your terrace--one that drains puddles !

Terrace rain gardens catch sidewalk runoff

.



On May 11, a hailstorm knocked maple flowers onto the pavement.  Rivulets traced patterns in the yellow flowers, showing where the runoff goes.  It's clear that most sidewalk runoff flows into the street, where it's flushed quickly by sewers to the lakes.

Trillium spectacle west of Madison !

How I became a woodland gardener

If you have lots of shade, and no money for plants--

here's an easy method.

Lake Mendota garden designed by Richard Fayram

.

Doug and Sherry Caves built two large rain gardens at their new house on Lake Mendota.  It's located at 2317 Middleton Beach Rd.

The gardens were designed by Richard Fayram--part of the entire landscaping when the Caves' new house was completed.  It sits on low-lying land, formerly a wetland bordering the lake.  Click on photos to enlarge.

The first garden is in the front, between the house and the street.  It takes runoff from the garage, and a small portion of lawn to the left.  Because the soil was compacted during construction, this one drains very slowly.  I saw two mourning doves use it for a bath, and the frogs like it.

Groundwater--unseen beneath our feet



About groundwater, its biology, and the springs about Lake Wingra.

Rain garden poster

Click on the image to enlarge.  You can order the poster here.  Purchase one and donate it to your school or library, to help spread the word.

Critters--"under the hood" of your rain garden

Rain garden critters 2--How do they survive between rains?

If you were to examine a little wet soil from your rain garden, and put a drop on a microscope slide, you'd probably see a lot of rotifers.  Barely bigger than amoebas, they still consist of many cells.

Rotifers...  Males are "degenerate*"--how cool is that?

art by Elizabeth Buchsbaum

Rotifers try "abstinence only"--for 30 million years

Our aim is to bring you the latest news--to help you appreciate our lakes and streams.  And what's more engaging than a rotifer?  Rotifers live in temporary pools of water, like your bird bath or rain garden.

Terrace rain gardens you can do yourself

Terraces--the space between the sidewalk and the street--are the wild west of city infrastructure.  The wide-open spaces.  They are a resource right under our noses, ignored by most.

Owned by the city, but within the personal space of homeowners, they are a delicate issue.  The city treads softly here.  But tread it must, for the good of the community.

My neighbor Bob Kowal, 537 Gately Terrace, has developed a novel kind of rain garden on his terrace.  Bob is a retired professor at the UW Botany Department.

If you look at his terrace garden, you wouldn't notice anything unusual, except that it's extremely luxuriant.  And it fills the entire terrace, from driveway to driveway.

A rain garden street for our neighborhood?

A guest article by Elizabeth McBride

Gardener extrordinaire

I used to think of a rain garden as a trendy “green” gesture, something you could pat yourself on the back for having but not all that effective in the scheme of things. Today my thinking changed.