1 © 2011 Regents of the University of Minnesota. All rights reserved. 11 RESIDENTIAL RAIN GARDENS...

1

© 2011 Regents of the University of Minnesota. All rights reserved.

11

RESIDENTIAL RAIN GARDENS

Gra

phic

: C

ity

of M

aple

woo

d

2

A rain garden is a

water-quality tool

that you can use

in your own yard.

3

© 2011 Regents of the University of Minnesota. All rights reserved.

WHAT WE’LL COVER What is a “rain garden”? Functions and benefits How to make one Plant selection Maintenance Cost Helpful resources

4

WHAT IS A “RAIN GARDEN”? A shallow sunken garden that recycles the rain

– less than 8” deep Rainwater runoff is directed toward it Runoff soaks in

Photo: Mary Nolte, Fulton neighborhood, Minneapolis

5

© 2011 Regents of the University of Minnesota. All rights reserved.

PLANTS HELP RECYCLE THE RAIN Plant roots

absorb water Water goes up

the stem Leaf surfaces release

moisture Water returns to

the atmosphere as a vapor

6

© 2011 Regents of the University of Minnesota. All rights reserved.

A RAIN GARDEN IS ALSO KNOWN AS ... Mini wetland Water quality garden Stormwater marsh Planted swale Bio-retention pond Strategically placed puddle

7

© 2011 Regents of the University of Minnesota. All rights reserved.

FUNCTIONS OF A RAIN GARDEN Diverts runoff from paved surfaces

– Driveways, roofs, streets, patios, walks Water moves “sideways” – runs off pavement

Keeps runoff on site– Instead of flowing untreated into streams and

storm sewers

Soil acts like a living sponge– Water moves “down” - into the ground

8

© 2011 Regents of the University of Minnesota. All rights reserved.

BENEFITS OF A RAIN GARDEN Soaks up 30% more runoff than lawns Filters polluted runoff

• sediments, fertilizers, pesticides

Recharges groundwater Helps prevent flooding Provides habitat/food for butterflies, birds Beautifies a low spot in the yard

9

POLLUTED RUNOFF HARMS WATER QUALITY

Flows into waterways untreated

Harms fish and wildlife

Kills vegetation Fouls drinking

water supplies Makes recreation

areas unsafe

10

EVERY CURB IS A SHORELINE

Grass clippings and leaves are the main source of phosphorus in lakes and streams

Rain gardens act as filters and remove:– 94% of sediment– 43% of phosphorus– 70% of nitrogen

11

© 2011 Regents of the University of Minnesota. All rights reserved.

DESIGN FEATURES ARE FLEXIBLEVariables include: Location Soil Size and shape Plants

12

© 2011 Regents of the University of Minnesota. All rights reserved.

www.montgomerycountymd.gov/mc/services/dep/greenman/rain.htm

© Fitc

h &

Co

.

LOCATION OF THE RAIN GARDEN

13

© 2011 Regents of the University of Minnesota. All rights reserved.

GO WITH THE FLOW Observe the drainage pattern in your yard Locate the garden:

– in a natural low spot– near sidewalks, driveways, or other paved surfaces– down-slope from roofs, gutters, downspouts, sump

pump outlet

Direct water into rain garden– channel or buried plastic pipe

14

Project and photo by Kestrel Design Group

15

Locate the rain garden at least 10 feet from the house, on a gentle slope

16

© 2011 Regents of the University of Minnesota. All rights reserved.

BIRD’S-EYE VIEW OF RAIN GARDEN LOCATIONS

Gra

ph

ic:

UW

Ext

en

sio

n S

erv

ice

17

© 2011 Regents of the University of Minnesota. All rights reserved.

TRADITIONAL PATH OF ROOF RUNOFF

Graphic: Applied Ecological Services, Inc.

18

Average runoff from a roof is 24,000 gallons per year

That would fill 600 bathtubs!

19

© 2011 Regents of the University of Minnesota. All rights reserved.

ROOF RUNOFF DIRECTED TO RAIN GARDEN

20

© 2011 Regents of the University of Minnesota. All rights reserved.

RAIN GARDENS IN HOME LANDSCAPES

In a back yard catching runoff from the garage

In a front yard catching runoff from a downspout

21

© 2011 Regents of the University of Minnesota. All rights reserved.

THE SOIL MUST DRAIN! A rain garden is NOT a pond. Percolation test:

– fill a 6-inch-deep hole with water– should drain within 24 hours– if not, don’t put a rain garden there– or amend soil

“Rain garden soil mix”– 50-60% sand, 20-30% topsoil, 20-30a% compost

22

© 2011 Regents of the University of Minnesota. All rights reserved.

HOW BIG? No standard size Rule of thumb: 1/3 of drainage area

– e.g., 170 sq. ft. (10’ x 17’) garden for 500 sq. ft. of drainage area

Factors include slope, soil type, distance from runoff point

Even a small rain garden is beneficial

23

© 2011 Regents of the University of Minnesota. All rights reserved.

CALCULATING DRAINAGE AREA Area of roof

going to down spout

Length of house 100 feet Width of house 20 feet L X W = 2000 sq ft 2000 sq ft ÷ 4 =

500 sq ft draining to the rain garden

Width

Length

Graphic: UW Extension Service

24

© 2011 Regents of the University of Minnesota. All rights reserved.

DESIGNING THE RAIN GARDEN Call Gopher State One: 800-252-1166 Outline it with rope or hose

curvy shape

Remove sod and dig to desired depth

25

© 2011 Regents of the University of Minnesota. All rights reserved.

DESIGNING THE RAIN GARDEN Features:

gently sloping sides flat in the deepest spot berm at low end grass filter strip on top edge mulch – shredded bark

26

© 2011 Regents of the University of Minnesota. All rights reserved.

A soil berm acts like a bumper – keeps water from flowing over edge

Photo: UW Extension Publication GWQ037Berm

27

RAIN GARDEN COLLECTS PARKING LOT RUNOFF

Photos & design:

Kestrel Design Group

Spray paint outlines the garden shape

28

Parking lot runoff

flows into the rain garden instead of into the street

Runoff pools in the garden, then seeps into the ground

Ph

oto

an

d P

roje

ct b

y K

est

rel D

esi

gn

G

rou

p

29

Graphic: UW Extension Publication GWQ037

BIRD’S-EYE VIEW OF A RAIN GARDEN

30

© 2011 Regents of the University of Minnesota. All rights reserved.

LAYOUT FOR A 140-SQ.FT. GARDEN

Graphic: UW Extension Publication GWQ037

31

Photos: Mary Nolte

Before

After

Buried pipe connects to downspout

Berm

32

© 2011 Regents of the University of Minnesota. All rights reserved.

PLANTS FOR RAIN GARDENS

33

© 2011 Regents of the University of Minnesota. All rights reserved.

SELECT PERENNIAL PLANTS THAT Tolerate both wet and dry spells

– plants that like wet feet in deepest part e.g.: Blue flag iris, marsh milkweed, big bluestem,

sedges, red-twigged dogwood, buttonbush

Tolerate de-icing salts (if near roads) Match up with soil and light conditions

34

NATIVE PLANTS HAVE ADVANTAGES

Adapted to the climate and native pests

Deep rooted– long roots make

channels in the soil for water to follow

Havens for butterflies, birds, beneficials

35

© 2011 Regents of the University of Minnesota. All rights reserved.

PRAIRIE PLANTS HAVE DEEP ROOTS

Graphic: Conservation Design Forum Inc.

36

© 2011 Regents of the University of Minnesota. All rights reserved.

RAIN GARDENS IN MAPLEWOOD, MN INSTEAD OF CURBS AND GUTTERS

Photo: City of Maplewood

37

© 2011 Regents of the University of Minnesota. All rights reserved.

SUN GARDENS

Photos: City of Maplewood

38

© 2011 Regents of the University of Minnesota. All rights reserved.

GARDEN FOR LIGHT SHADE

Photo: City of Maplewood

39

© 2011 Regents of the University of Minnesota. All rights reserved.

Shrubs: Annabelle Hydrangea American Highbush

Cranberry Anthony Waterer SpireaPerennials: Marsh Milkweed Stello d’Oro Daylily

AN EASY SHRUB GARDEN

Photo: City of Maplewood

40

© 2011 Regents of the University of Minnesota. All rights reserved.

MAINTENANCE Pull weeds (esp. the 1st year) Water ~3 x a week until established

– also during a dry spells

Mulch – shredded hardwood won’t float away

Cut back or mow down

41

© 2011 Regents of the University of Minnesota. All rights reserved.

WHAT ABOUT MOSQUITOES? A rain garden is not a pond No standing water between rainfalls Mosquitoes need at least 7 days in

standing water to hatch– will not survive if wetland dries out in less than

a week

42

© 2011 Regents of the University of Minnesota. All rights reserved.

ESTIMATED COST AND PLANTS NEEDED Do-it-yourselfers:

– about $3 to $5/sq. ft.

Professionals: – about $10 - $12/sq.ft

Plants needed for 300 sq. ft. garden– 100 for wet zones – 200 for upland zones

43

© 2011 Regents of the University of Minnesota. All rights reserved.

Shallow saucer shape Strategic location Plants match soil and

moisture levels Soil drains Size appropriate for

yard and drainage area

SUMMARY

Photo: Mary Nolte

44

© 2011 Regents of the University of Minnesota. All rights reserved.The University of Minnesota is an equal opportunity educator and employer. In accordance with the Americans with Disabilities

Act, this PowerPoint is available in alternative formats upon request. Direct requests to the Extension Store at 800-876-8636.

Discover more atextension.umn.edu