Rain Garden Basics

Deciding how to landscape for rain garden can be interesting. The landscaping method to choose depends on the lay of the land, what kind of water flow is happening at different times of the year, soil type,¹  and what the rain gardener might trying to filter out of the water.²   Rain gardens replenish under ground aquifers. Also the heat created in the flowing water pouring off roof tops is kept from over heating wild life.³

A well thought out landscape can divert pollution into the ground. This diversion can usually be accomplished by doing the work yourself (DIY) at home by converting a dig about six to eight inches down across the specified surface area.

When considering if the project needs a landscape rain garden professional soil type is an important factor to think about. Professionals, scientists, advanced hobbyists, and folks serious about rain gardening for food or art use the same chart for measuring how much water will soak down into the soil unaided.

The term hydrologic is used as a name for this chart.  It is a combination of two words:  Logic (thinking) and hydro (water).  Thinking about water in this case assumes that it goes without saying; that this thinking refers to how well the water soaks into the ground below the surface of the ground.

Often once the water starts saturating the ground it is referred to as "soak".

There are four basic types of soil.  Thinking about how well the water soaks in; a soil group is determined by how well the water penetrates the surface naturally.

The percentage to which each type of surface allows the water to saturate is referred to as that soil groups curve run off number.

 For soil types in the (HSG) Hydrologic Soil Groups⁴   first two divisions’ (out of four general points of reference in ‘run off curve numbers), a DIY project is generally doable.⁵   For the second two, a land caretaker(gardener) will want to hire a professional landscaper to create a functional rain garden.^{6 7}

‘DIY’, or ‘consult a professional landscaper’ groups:

• Group A: 10% clay; 90% sand, loam, silt, or combo; 35% or < rock rubble or fragments—absorbs 5.67 in. of rain fall per hour—more than 50 cm (20 in.) about to impermeable layer, water table > 60 cm (24 in.) down.

• Group B: 10-20% clay; 50-90% sand, loam, or combo; silt, or combo if they are low density and rock rubble fragments are 35% or <; > 50 cm (20 in.) to impermeable layer; > 60 cm (24 in.) to water table.

‘Absolutely Consult a professional landscape rain garden designer’ groups.  Because if your property is like this doing the project yourself is going to be too hard:

• Group C: Water transmission is visibly restricted; 20-40% clay; < 50% sand, > 50% loam, silt, or combo; > 35% rock rubble fragments; etc.,.

• Group D: Land that is nearly completely unobservant; extreme clay texture, and low silt combo; or harder; etc.,.

Reducing impenetrable surfaces around a home or property is one of the benefits of a landscaped rain garden. In Oregon, state and local governments offer a 7% tax credit that is multiplied by the square footage of impervious surface that has been converted to permeable surface.

Storm water is meant for the aquifer⁸  below. In modern society wells and rough run off diverted to the street have depleted these natural underground water ways in America,^{9 10 11} and around the world.^{12 13} Aquifers’ account for 29% of the world’s water supply: In perspective lakes supply us with 1%.¹⁴

Rain gardens return this water naturally filtered by soil to the overly exercised well base. This is referred to as ground water recharge.¹⁵

Rain gardens are also called bio swales when they occur naturally. A rain garden or a bio swale are both great ways to filter run off roof water, and house hold grey water back down to the aquifer. As the water flows and soaks into the ground the liquid H2O the temperature cools, and the soil filters out chemicals, and massive quantities of other pollutants. Went a bio swale is artificial, (meaning not a natural part of the landscape) the landscaped bio swale is called a rain garden.

A landscaped rain garden which is an artificially created bio swale is often decorative, and serves as a conservation,¹⁶ prevention,¹⁷ or soil retention¹⁸ method.

Some pollutants may be safe in small proportioned numbers, but in greater amounts the pollutant can be fatal for wildlife or flip the balance of the environment out of sink with the natural established role of different species and their habitat.

One of the first steps to remember during rain garden planning in order to create successful landscape is to look for the natural low point.

Next determine if the soak (water making its way into the garden and lower ground) will leak out of the soil at another point to create a problem in other areas, or for neighbors. Unpredicted runoff can occur if gravity and sub surface geology cause the water to resurface outside of the property line. This is not common, but it can occur. This is why having an experience rain garden landscaper is essential for property care takers who have a busy life style, or are inexperienced in landscape rain garden overflow planning.¹⁹ This is especially important for a rain garden planned by the rain gardener for a steeply sloped neighborhood.

Note; 

 Avoid: 

• Slopes of 12% or steeper 

• Tree base • Wells 

• Septic areas 

• Foundations 

• Tornado/ Bomb shelter 

• Neighboring property lines 

• Starting within two feet of a water table’s lowest year round elevation

In order to have good soil retention choosing beautiful native rain garden plants²⁰ that are natural to the region is essential,²¹ since the roots can grow from 5 to 10 feet deeper. Choosing a local landscape rain garden planner can shorten time of due diligence necessary to have a silt, soil, small stone, and sand project that drains well based on the pace of the snow melt,²² applied grey water,²³ and rain fall storm water run off.

Landscape rain garden (s) are rehydrating depleted aquifers’, preventing warm/boiled water run off that adversely change the natural temperature of fish habitat,²⁴ retaining soil due to the deep root system plant choice, filtering out pollutants’ from roadways, business parking lots,²⁵ and creating vibrantly elegant show piece yards across the Pacific North West.

[1] http://www.aacounty.org/DPW/Highways/RainGarden.cfm

[2] http://www.uri.edu/ce/healthylandscapes/raingarden.htm

[3] http://www.oregoncc.org/sustainability/  Matt Uchtman of the Oregon Convention Center talked about heated water from the roof and parking lots being cooled by the soil; before being diverted into the nearby river in a previous interview.

[4] http://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=17757.wba  Cf., Part 7 1-2 Part 630.0701 ¶ 1-5 National Engineering Handbook.

[5] http://seagrant.oregonstate.edu/sgpubs/onlinepubs/h10001.pdf

[6] http://soildatamart.nrcs.usda.gov/documents/SDMPurposeAndProcedures.pdf   Cf., Pg 7-15

[7] http://soildatamart.nrcs.usda.gov/

[8] http://en.wikipedia.org/wiki/Aquifer

[9] http://waterquality.ifas.ufl.edu/Water%20primer/Underground%20water/Underground.htm

[10] http://en.wikipedia.org/wiki/Ogallala_Aquifer

[11] http://academic.emporia.edu/schulmem/hydro/TERM%20PROJECTS/Musgrove/Basin_Range.htm

[12] http://academic.evergreen.edu/g/grossmaz/WORMKA/

[13] http://environment.nationalgeographic.com/environment/freshwater/groundwater/

[14] global.wisc.edu/outreach/k-12/webb/units/aquifer-summary.ppt

[15] http://waterquality.ifas.ufl.edu/Water%20primer/Underground%20water/Underground.htm#Groundwater 2

[16] http://www.maricopa.gov/ENVSVC/WATER/DRINKING.ASP

[17] http://www.groundwater.org/

[18] http://www.unep.org/Themes/Freshwater/PDF/Rainwater_Harvesting_090310b.pdf   Sec 1. Pge 5: cf., sec1:5.

[19] http://www.asla.org/awards/2007/07winners/517_nna.html

[20] http://emswcd.org/raingarden

[21] http://emswcd.org/oregon-native-plants

[22] http://en.wikipedia.org/wiki/Scupper

[23] http://www.rain-barrel.net/make-your-own-keyhole-garden.html

[24] http://www.gvsu.edu/wri/director/rein-in-the-runoff-stormwater-integrated-assessment-in-spring-lake-stormwater-education-23.htm