Slow The Flow: 5 Easy Steps

Winter is upon us, and so, too, are the winter rains. Many years ago, much of present day Thurston County was forestland. Nearly half of the fallen rain was intercepted by branches and leaves. The rest would slowly soak into spongy soils where the roots of trees and shrubs held the soil together and drank up much of the water.

Today the rain that falls on our roofs, driveways, compacted lawns and other hard surfaces quickly runs off into ditches and pipes that empty into streams, lakes and Puget Sound. This stormwater runoff picks up pollutants along the way, such as dirt, oil, metals, pet waste and chemicals from lawns and gardens. Also, stormwater runoff increases stream flow, causing flooding, and scouring and eroding of the stream banks and bottom.

On your own property, try to “slow the flow” by infiltrating the rain that falls on house and yard back into the ground. By following these 5 easy steps, you can mimic the natural forest water cycle right in your own yard!


1. Plant Trees
Trees and shrubs catch into the atmosphere. Their roots loosen the soil, thereby improving infiltration, or water. A single mature tree with a 30 foot crown can intercept over 700 gallons of rainfall each year.

A single mature tree with a 30 foot crown can intercept over 700 gallons of rainfall each year.

2. Improve Soil with Compost and Mulch
Improve Soil with Compost and Mulch – Improving the health of your soil by mixing in compost or mulch will also help more rainwater soak into the ground. It can also help you save money by reducing your summer irrigation needs because grass and other plants will grow deeper roots and the soil will hold more water.
To amend existing lawns, aerate in the spring or fall, and then rake in ¼ to ½ inch fine compost and/or mulch mow. When you mulch mow (leave clippings on your lawn), you encourage your lawn to grow deeper roots, which improves your lawn’s resistance to drought and improves soil health.
3. Disconnect Your Downspout*
If your downspout currently flows to the stormwater system (drainage ditch or stormdrain), then you may be able to redirect the runoff into a landscaped area, rain garden or rock-filled trench.
4. Install a Rain Garden
Rain gardens are shallow depressions that can hold and infiltrate runoff from your roof, driveway and other hard surfaces. They have compost-amended soils and are landscaped with plants that beautify your yard while soaking up and filtering runoff. Thurston County and the City of Olympia are both offering $200 reimbursements for installing rain gardens. For more information turn to page 7.

Stream Team will be co-sponsoring a free Rain Garden Workshop along with WSU Native Plant Salvage Project in April 2013. For more information, visit and click on the calendar or call 360-867-2167. To download a FREE copy of the Rain Garden Handbook for Western Washington Homeowners or to view a rain garden installation video go to

5. Rock-Filled Trench*
Install a Rock-Filled Trench* – Rockfilled trenches can hold and slowly infiltrate runoff in areas that are too narrow for a rain garden.