Rain Gardens
What is a rain garden?
A shallow depression, planted with native perennials designed to collect
rainwater from rooftops, sidewalks, driveways, and other hard surfaces.
Why are rain gardens important?
American Waterworks estimates in a 24 hour period during an average
storm event over 700 gallons of water falls on roof tops! Where does
all this water go?
 According
the EPA stormwater contributes to 70% of pollutants in streams.
Rain
gardens help to improve water quality by retaining water from these
surfaces that contain sediments, fertilizers, pesticides and other
chemicals and allowing it to slowly percolate into the soil instead
of flowing into storm sewers and eventually into water bodies.
Other benefits to a rain garden
- They attract wildlife to your property
- Once established, they require little maintenance- no fertilizers
or pesticides
- They provide color and interest to your landscape
Selecting a site
Use the existing drainage pattern of your property
- Look where your water drains after it rains
- Identify low spots where water collects
- Keep in mind that your rain garden will be dry most of the time,
and when wet the water will be at the surface for about 2 days.
There is no need to worry about mosquitoes; the garden will not
be wet long enough for eggs to hatch
If you don't like the location of the low spots on your property,
you can create your own area by excavating. Choose a site that is
close to where you want to capture the water (i.e. driveway, downspout).
- Hints
- Don't place rain gardens too close
to your foundation, or you may end up with a leaky basement.
Choose at site at least 10 feet away
and downslope from your foundation
- Be aware of underground utilities. Call Miss Dig before
doing any excavating.
- If you choose a site where water does not naturally drain
to, there are several solutions for diverting
the water.
Evaluating the soil
You need to understand your soil's fertility, drainage, and pH.
Soil test kits can be purchased for a small fee from MSU Extension.
They will test the pH, nutrient content & soil type. They will
also provide recommendations on how to improve your soil.
To test for drainage, dig a hole 8” deep and fill the hole with
water. The hole should drain 1” per hour, if it drains any slower
than that you have a lot of clay in your soil and you will need to
amend it.
If you choose to replace all of the soil in your rain garden, you
should replace it with 50-60% sand, 20-30% topsoil, and 20-30% compost. Be
sure no clay is in your replacement soil.
In urban areas, soil may be compacted. For the rain garden to absorb
as much water as possible, loosen the soil to a depth of 2 feet.
Designing/Preparing your site
 Typically
sized rain gardens for a single family home are between 150-400 square
feet
Select the shape of your garden. You can use hose to outline the
border or non-toxic paint, available from landscape contractors,
to draw your border. If there is turf within your border, you will
need to remove it.
Once the turf is removed, you can begin digging your hole. The
West Michigan Environmental Action Council, recommends that if you
are not replacing your soil, you double dig to a depth of 2 feet.
If you are replacing the soil, you should replace it with 50-60%
sand, 20-30% topsoil, and 20-30% compost.
– To figure out how
much soil use this formula:
- 1 cubic yard=27 cubic
feet.
- A rain garden that is 2 feet deep X 5 feet wide X 10 feet
long will need 100 cubic feet of replacement soil, or about 3.7 cubic
yards.
Grade the garden area so that water entering it can be spread out
over a wide area. You can make the grade gradual, with the center
area of the garden 6” deep and the edges graded gradually to the
center.
Selecting Your Plants
We recommend you use native perennial plants for your rain garden.
Native perennials are adapted to Michigan's climate.
They have
deep root systems which allows the plants to get water even during
drought.
Many
insects and animals depend on them as a food source.
Native Perennials for Full Sun
Native Perennials for Full of Partial Sun
Perennials for Full/Partial Sun or Full Shade
Perennials for Partial or Full Shade
Perennials for Full Shade
Trees/Shrubs for Rain Garden
Planting Your Rain Garden
Choose the right plant for the right place. Take into consideration
light & moisture requirements.
- There are three zones in a rain garden:
- Zone 1: Very Wet (center of garden)
- Zone 2: Wet to Dry (plants around the center)
- Zone 3: Dry (plants along the edge)
- Pay attention to mature height. Taller plants may not work
if they will block views to roads. If using tall plants put them
in zone 1 or at the back of the garden and plant smaller perennials
in front of them.
Plant one plant per square foot.
Once plants are in the ground, water thoroughly and mulch with a hardwood mulch.
Mulch will help the soil conserve moisture and reduce weed competition.
Maintenance
If it does not rain during the first year, water your plants thoroughly
during the first year until they become established.
Place rocks in areas where strong water enters into your rain garden
to help reduce erosion that can remove soil, mulch and plants.
Weed regularly. Visit www.NPS.gov if
you have problems identifying invasive weeds.
Monitor your plants. If they are not doing well in a particular
location, move them.
Wet Basements
Why is your basement wet? This may be for a number of reasons, such
as:
- water infiltration
- geographic reasons
- various types of soil
- the nature of the water
Over 60% of houses in the US have wet basements.
What Makes the Basement Leak?
The footings are continuous slabs that the foundation walls are
built on. They bear the weight of the house on the soil. The footings
are poured on tight undisturbed virgin soil. They are generally
twice the thickness of the wall and about 10" thick.
Foundation walls are built on the footings. They are most commonly
made of poured concrete or concrete block. Stone walls were built
without footings.
Since the concrete footings cured before the walls were built, the
two never become one piece of concrete. The joint left between the
footings and walls is called a "cold joint."
The outside of the foundation walls may be coated with "foundation
coating," which is a loose tar that is brushed or sprayed on (like
driveway sealer). This coating is classified as "dampproofing," not
waterproofing.
Over time the solvents in it dry out and it deteriorates, letting
water pass. Additionally it is not flexible and won't bridge any
cracks from shrinkage, settlement, or movement.
If backfilling (filling the space between the dirt and the basement
wall) is done incorrectly,
such as in one day and with the wrong materials, water pressure could
build up around foundation walls.
Causes of Drainage Problems
Wetness and water problems may have been caused by:
- Flooding
- Seasonal high water table
- Surface ponding & runoff
- Slow soil permeability
- Springs and seeps
Flooding
If your home is in a flood plain or close to a stream or creek:
- There is a risk of flooding if the stream overflows during heavy
rainfall or rapid snowmelt.
- Even if you have taken precautions to flood proof your home,
you can
never totally eliminate the potential for flooding, but
you can
reduce flood damage.
You can prevent flooding damge by making your home more resistant,
which includes: measures that block openings such as windows and
doors, regulation of drain outlets, and water proofing walls.
If your house is near a stream, make sure the site is not in the
flood plain by checking with the local building department for flood
plain maps.
Seasonal High Water Table
If the water table is 6 ft. deep or more, high
water table problems will be minimal.
When the seasonal water table is less than 6 ft. from
the surface, a sump pump with a system of foundation
drains and/or a wellpoint system should be used to lower the water
table.
Create a good outlet for discharge flow into the pump by installing
gravel and drains around the base of the outsite walls.
Surface Ponding
If a significant amount of surface water ponds on your lawn or driveway
for long periods, install small diversions to channel off the water.
Even in upland areas, a continually wet basement or flooding can
occur if the house is built in the path of a natural drainage way,
in a pothole, or if the site is lower the surrounding area.
In developed areas where the landscape has been greatly modified,
runoff is increased and natural drainage ways are often
blocked or altered.
If man-made drainage ways or storm
sewers are not built to carry this additional
seasonal water flow, nearby homes may flood or
experience surface ponding.
To remedy this hazard, grade the yard (a
minimum grade of 1 foot in 100 feet), so that
surface water drains away from the house.
When
filling low areas use the most
permeable
soil available. Save the top
soil
and spread it over the newly filled
and graded
areas to help establish
vegetation. To
reduce soil compaction, limit construction traffic on the lawn.
Installing roof gutters and downspouts to control roof water may
prevent ponding in low yard areas.
Downspouts can empty into spreaders that discharge water in a thin
layer over a grassy area.
Springs and Seeps
On many sites, natural springs and seeps occur due to existing geology
and landscape characteristics.
Water may flow seasonally, throughout the year, or may flow into
or around homes constructed over or near a spring or seep.
For protection, install subsurface drains at least 4" in diameter
surrounded by 6-12" of gravel or sand. Place
gravel along the outside of the base of the foundation wall.
Install an adequate gravity or pump outlet for the tile pipe. An
interceptor drain can divert seep or spring water before it reaches
the structure.
Typically, subsurface drains are made of plastic, but older drain
tile may be made of clay, concrete or metal.
Simple Solutions
- Downspout water should be directed away from your house.
- Grade the ground adjacent to the foundation
walls so that it directs water away from the house.
- If controlling surface water does not help, the problem may be
below the surface - a high water table, spring, or seeps etc.
Soil Characteristics
Sand
- Low nutrient-holding capacity
- Little plasticity (capacity to be molded or altered, putty-like)
or stickiness
- Large pore space between particles
- Low water holding capacity
- Good water percolation and drainage
- Good aeration
- Low exposed surface area
Clay
- High exposed
- Small pores between particles, but high in total
- Highly plastic (capacity to be molded or altered, putty-like)
and sticky
- High water-holding capacity
- Slow water and air movement
- Poorly aerated
Silt
Gravel
- Gravel is crushed stone
- It does not hold water
- Very good water percolation and drainage
- Highly aerated
- Fast water and air movement
Slow Soil Permeability
If the soil has a dense layer of clay or severely compacted layer,
water flow through the soil may be restricted causing ponding.
Using a soil aerator or deep rooted native grass helps increase infiltration.
For larger wet areas, install subsurface drains about 4 inches
in diameter at a depth of 2 to 5 feet.
Use sand and gravel to backfill the drain trench to within a foot of the ground
surface.
The Nature of Water
"Water flow within porous concrete before,
during, and after the coating has been applied is one of the major
causes of problems associated with foundations." - Permanent Buildings & Foundations magazine
Sign of Structural Deterioration
Efflorescence (seen in the picture at
right) is the white crystalline deposit that forms on the surface
of concrete. This is the chemical breakdown of the bonding agent
that holds your walls together.
Cracked walls are a sign that the foundation has
moved/shifted. These should be inspected to determine the exact cause.
Peeling paint is a sign that the wall has taken
moisture inside, as paint will not stick to a wet surface.
Rust on appliances or furniture:
look for rust on bottoms of furnaces, water heaters, and other metal
appliances.
Rust is a sign of dampness and water evaporation.
Dry Rot and dark brown/black
fungus. Grows on walls
and other surfaces. Grows mostly on wooden surfaces, causing wood
to decay.
Warped Paneling is caused by moisture
that makes paneling bow and discolor,
commonly at the bottom portion of the paneling.
Consequences if Unsolved
- Mold/and or mildew
- Fungus that grows in damp, dark areas
- Causes discoloration
- Musty smells and odors
- Musty odors
- This is the result of the decay process from mold, mildew,
and dry rot
- Damp spots on the wall
- A sign that water has absorbed through the wall
- Block will have dark grey splotches in various places
Diagram of soil pressure on foundation walls
Stages of Silting
Stage 1
- Mold/Mildew and Fungus
- Dampness-discoloring
- Odors-Rust
- Aggravation of allergies
- Respiratory ailments
Stage 2
- Excessively damp
- Hairline cracks
- Spots on walls
- Loss of lime salt (white powder from walls)
Stage 3
- Puddles on the floor
- Basement seepage during moderate rain
- Basement flooding during torrential rains
- Electrical shock hazard
Stage 4
- Walls bowing or buckling
- Visible mud or clay silt
- Corners shifting and cracking
- Floor dropping
- Visible structural damage
- "House is on the move"
Keeping a Basement Dry
The best waterproofing barriers are a membrane coating (a three
layer system) or plastic film. Before such a barrier is applied,
any visible cracks should be sealed with an expansive cement. Walls
must be thoroughly cleaned before using a membrane coat. When plastic
film (usually heavy-gauged polyethylene) is used as a barrier, it
is applied in overlapping sheets and sealed with an adhesive.
Waterproofing the foundation walls is only the first step; you also
need a system of drains around the foundation that silt will not
render useless.
Rigid-foam protection board shields the membrane from backfill damage.
Applied while the waterproofing is still tacky, the 1/4" foam panels
also provide a thermal break between the foundation and backfill.
Waterproofing, not dampproofing, seals the foundation walls. More
expensive than asphalt based mixtures, a rubber-based membrane sprayed
onto foundation walls remains flexible and waterproof.
Bad Waterproofing [:25 , 493 KB WMV]
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For further information about waterproofing your basement, and products,
visit the Basement Systems© website.
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