Rain and Runoff


Staff Report

Rain gardens are an attractive and cost-effective way to treat and manage storm water. Courtesy Pierce County

The Shellfish Partners, Special to KP News

Around here, rain happens—a lot. But did you know that how you manage stormwater runoff on your property could make your life easier, your animals healthier and the streams that feed Puget Sound cleaner? With a few simple steps, you can improve muddy paddocks, wet basements, soggy garages, overflowing culverts, eroding ditches and mushy lawns.

The first step is to absorb as much rain as possible. Trees are ideal. A mature tree can absorb 36 percent of the rainfall it comes in contact with. Plants and shrubs can increase the rain absorption rate even more. Mature forests have surprisingly little runoff, even in very rainy areas.

Another option is to send excess runoff into the ground. Dry wells and rain gardens can help. A dry well often drains to a large pit in the ground, which is filled with gravel. A rain garden is a low spot in your landscape designed to catch storm water and filter out pollution.

Plants absorb water, slow down flow and filter pollutants. Lawns and ivy are the exception to this rule. Ivy doesn’t have the erosion-prevention attributes of other plants. You can look beneath ivy and often find an eroding slope. Manicured turf does not infiltrate as much runoff as plants and trees, and maintenance practices can exacerbate problems. Typical lawn care practices include blanketing large areas with chemicals and adding even more water to those surfaces. Since lawns are attractive places for dogs and Canada geese to defecate, that extra runoff can carry a lot of bacteria.

Paved surfaces are a challenge because rain runs off quickly, hitting ditches and streams all at once, overwhelming them and causing erosion. Pavement can also carry motor oil and other pollutants. If you have pavement, put some thought into directing runoff carefully, away from foundations, garages, septic system drain fields, animal-keeping areas and exposed earth. If you can, direct your runoff through a vegetated area to slow and filter it before it leaves your property. Remember that runoff from your property can cause damage to neighbors’ yards or pollute roadside ditches or streams. If this happens, you are responsible for damages and resulting pollution.

Exposed dirt can cause its own set of problems. Runoff picks up loose soil and carries it away. This is often topsoil that you want to keep. Place gravel or rock over high-traffic areas and plant grass or hardy groundcover over lighter-use areas.

Finally, if you need to install culverts under driveways, size them generously. A large storm can cause water to back up behind a small pipe and wash it out. This can cut off access to your home and cause problems for properties downstream.

Want help—for free? Schedule a courtesy inspection with Pierce County Public Works staff for technical support on drainage problems: 798-2725. If you have animals, the Pierce Conservation District can recommend management practices to control mud and keep your animals healthy: 845-9770.

The Shellfish Partners have been at work to protect Key Peninsula’s beaches and shellfish resources since 2006. Made up of Pierce County Public Works, Pierce Conservation District, Tacoma-Pierce County Health Department, community organizations and Key Peninsula residents.o learn more or to get involved, call 798-6470 or visit www.tpchd.org/shellfish.