Drainage Issues in the Landscape
Master Gardeners
Virginia Cooperative Extension
Prince William County
Lorrie Andrew-Spear
Frank Reilly
Drainage Issues in the Landscape
• A. Where does the water come from and why
doesn’t it go away?
• B. Impact of drainage problems
• C. Drainage solutions
• www.AdvancedMasterGardener.org
PAGE 2
A. Where does the water come from
and why it doesn’t go away
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Precipitation, ground water, surface water
Watersheds
Physiographic regions and soil types
Soil texture and structure (particle sizes, pore
spaces, well-drained soils vs. not, organic
component, compaction)
• Soil horizons and water infiltration
• Run off (erosion, potential pollutants)
PAGE 3
Precipitation, ground water, surface
water
PAGE 4
Groundwater – Surface Water
PAGE 5
Run off affected by:
•Impervious surfaces
•Slope
•Vegetation
•Previous moisture
•Infiltration rate
PAGE 6
Run Off
•Flooding
•Erosion
•Potential pollutants
PAGE 7
Physiographic regions and soil types
• Physiographic Regions describe land surface
features
• Closely related to geology
• Slope, and soils are related
PAGE 8
Physiographic Regions
Appalachian Plateaus
Valley and Ridge
Blue Ridge
Piedmont Plateau
Coastal Plain
PAGE 9
Soil Structure
Granular
Blocky
Prismatic
Platy
Columnar
Single
Grained
Massive
P A G E 10
Soil Texture
P A G E 11
Soil Texture
•Sand are the largest particles and they feel "gritty."
•Silt are medium sized, and they feel soft, silky or "floury."
•Clay are the smallest sized particles, and they feel "sticky" and
they are hard to squeeze.
Sand 2.00 - 0.05 mm
Silt 0.05 - 0.002 mm
Clay < 0.002 mm
P A G E 12
Pore Spaces
•The smaller the
particles
•The smaller the pore
spaces
•Water moves slowly
•Less air present
P A G E 13
Pore Spaces can decrease due to
compaction
P A G E 14
Soil horizons and water infiltration
•Horizons have different
properties
•Some may retard water
flow
•Watch out for the
“builder’s horizon”
P A G E 15
Check for Yourself
•Dig a hole 12 inches
deep and fill it with water
•30 minutes, the soil has a
drainage problem
•24 hours, waterlogged
soils may impact plant
growth
P A G E 16
Drainage Issues in the Landscape
• A. Where does the water come from and why
doesn’t it go away?
• B. Impact of drainage problems
• C. Drainage solutions
P A G E 17
B. Impact of drainage problems
• Home damage
• Puddles (mud, mosquitoes)
• Eroded topsoil, rills, gullies
• Lawns and plants (stressed – drowned)
P A G E 18
Impact of drainage problems
Home Damage
P A G E 19
Impact of drainage problems
Puddles
•Mosquitoes
•Mud
•Further damage
P A G E 20
Impact of drainage problems
Eroded topsoil, rills, gullies
P A G E 21
Impact of drainage problems
Erosion – Where do you think it goes?
P A G E 22
Impact of drainage problems
Lawns and plants (stressed drowned)
P A G E 23
Impact of drainage problems
• Damage at your home
• Damage Down Stream
– Watershed level
– Neighborhood level
• Keep the water safely on your property
P A G E 24
Drainage Issues in the Landscape
• A. Where does the water come from and why
doesn’t it go away?
• B. Impact of drainage problems
• C. Drainage solutions
• Drainage Options
P A G E 25
Drainage Options
1. Horticultural ways to help wet
soils
2. Slowing/intercepting Runoff
3. Slope/grading possibilities
4. Underground/subsurface
alternatives
P A G E 26
Drainage Options
Horticultural Improvements
• Soil
• Plants
• Mulch
P A G E 27
Drainage Options
Soils
• Add compost – organic matter
• Encourage earthworms/microorganisms
• Aerate lawns
• Avoid
compaction
P A G E 28
Drainage Options
Plant Selection
• “Wet Feet”
• Erosion control – groundcovers on slopes
• Native plants
• Plant lists:
- Extension Publications: Trees for Problem Landscape
Sites: www.ext.vt.edu
- Native plants for Conservation, Restoration and
Landscaping (comprehensive list):
www.dcr.state.va.us/dnh/native.htm
P A G E 29
Native Plants
• Group several of the same plant together to
establish a healthy population.
P A G E 30
Planting Wet Spots
Plants
Spiderwort
Cardinal Flower
Ferns
P A G E 31
Plants for Wet Sites
Plants
•Royal fern, maidenhair fern,
ostrich fern
•Cardinal flower
•Foam flower
•Bleeding heart
•Soloman’s seal
•Butterfly weed
•Columbine (native variety:
Aquilegia canadensis)
•Heavy metal switch grass
P A G E 32
Plants
Shrubs
• Sweet pepperbush (Clethra alnifolia)
• Red twig dogwood
• Bush blueberry (Vaccinium
corymbosum)
• Inkberry holly (Ilex glabra)
• Winterberry holly (Ilex vertilulata)
• Arrowwood Viburnum (Viburnum
dentatum)
• Sweetspire (Itea virginica)
• Red Chokeberry (Aronia abutifolia)
P A G E 33
Planting Wet Spots
Shrubs
Sweetspire
(Itea)
Winterberry Holly
Sweet Pepperbush
(Clethra)
PHOTOS: Floridata.com
Sweetshrub
(Calycarpa)
(Ilex verticillata)
P A G E 34
Plants
Trees
• River Birch (Betula nigra)
• American Hornbeam (Carpinus
carolinia)
• American Holly (Ilex opaca)
• Sweetbay Magnolia (Magnolia
virginiana)
• Tupelo (Nyssa sylvatica)
• Swamp White Oak (Quercus bicolor)
• Pussy Willow (Salix discolor)
• Bald Cypress (Taxodium distichum)
P A G E 35
Planting Wet Spots
Trees
Sweet Bay
Magnolia
American
Holly
River Birch
PHOTOS: Floridata.com
Hornbeam
P A G E 36
Planting Wet Spots
Odd Ball Plant collections
P A G E 37
Need More?
• Iris louisiana
P A G E 38
Drainage Options
Mulch
• Organic – bark, shredded or “nuggets”
– Different needs for drainage mulch!
• Depth of 2-4 inches
• Advantages
– Breaks raindrops/prevents erosion
– Aesthetic
– Weed control
• No volcanoes!
P A G E 39
Drainage Options
Slowing/intercepting Runoff
• Gutters/downspouts,
splashblocks/extenders
• Rain Barrel/cistern
• Rain garden
P A G E 40
Drainage Options
Gutters/downspouts
– Leaf guard to
prevent
stoppages
– Repair leaks
– Check slope
P A G E 41
Drainage Options
Splashblocks/
extenders
– Slope AWAY from foundation
– Extend downspout: roll-out,
perforated extension (above
ground or buried);
solid pipe
– Drop inlet
P A G E 42
Drainage Options
Rain Barrels &
Cisterns –
above or
underground
P A G E 43
Roof Top Rainwater Harvesting
P A G E 44
Rain Barrels have a number of uses!
P A G E 45
Drainage Options
Rain
Gardens:
Shallow landscaped
areas built to slow
down and hold
rain runoff, allowing it to soak into the
ground, instead of flowing into storm
drains.
P A G E 46
Rain Gardens:
Commercial Use
• Parking Lots
• Neighborhood Common Areas,
Parks, Schools
• New Commercial Developments
(LID)
P A G E 47
Drainage Options
Rain Garden Advantages
• Prevent Erosion
• Help prevent local (yard) flooding.
• Soak up to 30% more water than lawns.
• Prevent pollution
P A G E 48
Where to Build a Rain Garden
• Between area to be drained (roof, driveway or
yard) and storm drain or street
• Where downspout or other area can drain to it
across a grassy area, or “filter strip”
• At least 10 feet from your house’s foundation
• An oval or oblong shape approximately 5-7% of
the size of the area draining to it (roof, etc.)
P A G E 49
Testing Drainage
• Dig test hole
• One foot deep
• One foot long/wide
• Fill with water until saturated
• Fill again to top and let stand
• If doesn’t drain in 24 hours, the site is not
suitable for Rain Garden
P A G E 50
Building Rain Gardens
•Call Miss Utility!!!
•Remove grass and 3-6+
inches of soil to make a
level bottom.
•Mix in compost, sand,
topsoil, and other soil
conditioners for better
drainage.
P A G E 51
Rain Gardens
P A G E 52
Drainage Options
Slope/re-grading possibilities
• To slow and/or redirect flow of
runoff
But BEWARE: Don’t create more
problems for yourself or your
neighbors
P A G E 53
Drainage Options
Slope/grading possibilities
– Filling low spots
– Terracing slopes
– Swales and berms
– Dry creek beds
P A G E 54
Drainage Options
Filling low spots
– If adding soil to low areas – be
sure water has somewhere to go
– Incorporate the new soil
P A G E 55
Drainage Options
Terracing Slopes
– Prevents runoff erosion of slopes
– Makes better planting beds – level,
more stable
P A G E 56
Building Terraces
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Height
Materials
Reinforcement
Plants
Mulch
Terraces can work for
drives too
P A G E 57
Drainage Options
Berms
• Earthen mounds
used to direct
drainage (among
other uses)
• A site designer
should evaluate the
entire site’s
drainage before
considering a berm
of significant size.
P A G E 58
Drainage Options
Swales:
• Shallow
earthen
channels
covered
with grass
P A G E 59
Building A Dry Creek Bed
• Mimic stream’s shape – meander?
• At least twice as wide
as deep (good size
is three feet wide by
18 inches deep)
• Add rocks/plants
• Lead to dispersal area
or pond (NOT street)
P A G E 60
Drainage Options
Underground/subsurface
alternatives
• Hire Assistance for underground
drainage options to ensure proper
diversion and dispersal of water:
– French Drain
– Underground drainage system
P A G E 61
Drainage Options
French Drain
• Gravel-filled
trench
• Perforated pipe
• Covered with
fabric
• Slope to aid drainage
• Call Miss Utility FIRST
P A G E 62
Drainage Options
Underground Drainage System
• Hire a professional contractor qualified to
create drainage systems.
P A G E 63
BEST APPROACH
• Use as many options as you can get from the
tool box.
P A G E 64
Questions?
• www.AdvancedMasterGardener.org
P A G E 65