Rain Gardens

By Lani Walker

During the course of my Master’s work, I have the opportunity to take a class in Sustainable Landscape Practice this semester as an Elective.  I am hoping this Elective will help me in my Thesis work, which uses the outdoors as a classroom itself.  For the second week of class, we are studying Rain Gardens; gardens which are designed to capture and hold rainwater which would otherwise be surface runoff water.  I had never heard of a Rain Garden before this particular lecture, and I found it to be a very interesting and innovative solution for runoff water.  The project I decided to study in depth was a residential Rain Garden in Falls Church, Virginia.  The Rain Garden is located in the backyard to collect water directed from the home’s gutter downspout.  It appears that the homeowners built the Rain Garden without the assistance of a contractor.  The homeowners Rain Garden serves as the model in the guide, Rain Garden Design and Construction: A Northern Virginia Homeowner’s Guide.   It is stated in the above document that many of the techniques shown were taken from an earlier document, the Rain Garden Manual for Homeowners: Protecting Our Water One Yard at a Time by the Geauga Soil and Water Conservation District and the Northeast Ohio Public Involvement Public Education Committee. 

            This Rain Garden in Falls Church, Virginia was built to use the surface runoff water down a small slope in the backyard to water the garden and redirect the water to a storm sewer.  The homeowners sized the Rain Garden based on how much storm water they wanted to treat.  The Rain Garden was shaped to be wider than it is long, with the width perpendicular to the flow of the runoff.  The Rain Garden was created by digging into the sloped area to create a level area for planting.  Then, the underdrain was placed several inched below the surface.  The underdrain was surrounded on all sides with a thin layer of pea gravel.  The excavated soil (or engineered soil) was used to fill the planting area.  To prevent erosion, they immediately seeded the berm and covered the area with straw while the grass took root.  The soil was then ready to be used for planting the native plants.  Once the plants were planted, the area was mulched and the Rain Garden was completed.  Below is part of the case study I did on this particular Rain Garden, but the information could be applied to most Rain Gardens in general.   

ENVIRONMENTAL BENEFITS of the Rain Garden:

The Rain Garden will capture and hold rainwater which would have otherwise became surface runoff.  The Rain Garden is covered with mulch, which filters out pollutants in the rain water and protects the underlying soil.  Using native plants in the Rain Garden can provide a habitat and food for native species.

AESTHETIC BENEFITS:

The Rain Garden enhances the backyard because it will give the area more visual appeal.  Also, it is possible that the Rain Garden will attract butterflies and hummingbirds, which make the backyard an enjoyable place to site and view.  From the pictures, the backyard appears to have more landscaping surrounding the house, therefore, having a Rain Garden within the backyard will unify the site.

FUNCTIONAL BENEFITS:

Aside of the environmental purposes, this example doesn’t seem to have any functional purpose for the homeowner other than collecting and filtering water. 

SOCIAL BENEFITS:

This example improves the social atmosphere because it is in the backyard, a highly visible place where people generally have gatherings.  The Rain Garden makes the area more peaceful and enjoyable for the homeowners and guests.

EDUCATIONAL BENEFITS:

Since it appears that the homeowners used a How-To guide to create the Rain Garden, the building process became a learning experience for the homeowners and neighbors. 

Additionally, this example was used to create another guide for Northern Virginia.  Therefore, this project is a model for the public who are wishing to build a Rain Garden from the Rain Garden Design and Construction: A Northern Virginia Homeowner’s Guide.

ECONOMICAL BENEFITS:

It appears that the homeowners built the project without a contractor, therefore, they saved money by doing the project on their own.  It is difficult to determine the long term financial benefits of this particular Rain Garden, however, using native plants need less water and fertilizer once they are established (which save the homeowner money long term).

PSYCHOLOGICAL BENEFITS:

I have read that psychologists say gardening is a calming pursuit; therefore the maintenance of a Rain Garden could improve the psychological well-being of the homeowners.  Also, the Rain Garden could serve as a place in the backyard where people can sit near and relax.

CONSTRUCTION DETAIL:  Below is a quick sketch of how the Rain Garden preforms.

Image 1:  Section through the Rain Garden.  By:  Lani Walker

I found the idea of Rain Garden very interesting and now when I am on campus, I see many areas where this solution could be used.  In the future, I might even want to build one!  The sources I used for this information are below.

Rain Garden Design and Construction: A Northern Virginia Homeowner’s Guide

http://www.fairfaxcounty.gov/nvswcd/raingardenbk.pdf