Rain barrels and rain gardens do Watkins Creek good

We all know that when rain falls on our yards, parks, and gardens, it soaks into the ground (at least, we hope it does). But what happens to the rain that lands on roofs, driveways, parking lots, and roadways?

When rain falls on hard surfaces like these, it runs downhill along the surface. Rain falling on a roof eventually enters a gutter and then a downspout. After leaving the downspout, if the water hits another hard surface like a driveway or parking lot, it runs downhill along that. Unless these hard surfaces drain onto a planted surface, eventually that water drains into a storm sewer. From there, the water drains into a stream - into Watkins Creek if it falls in Watkins Creek’s watershed.

Allowing rainwater to drain into storm sewers and then into Watkins Creek helps keep streets and parking lots from flooding. But it isn’t so good for the creek. All that water entering the creek in a short period of time causes the creek to rise too much and too fast. The too-fast flow erodes the sides of the creek, eating into your backyard if you live along the creek. Your backyard soil may clog the bottom of the streambed when the flow slows down and the soil settles out. The soil might smother small insects, which would otherwise serve as food for fish. The creek loses quality and causes losses to property owners.

You can help reduce the amount of stormwater that enters Watkins Creek and obtain free water to use on your yard or in your garden by putting a rain barrel under one or more of your downspouts or by creating a rain garden on your property. A rain barrel is a large container that sits under a downspout to collect rain that flows off a roof. The container has a hose bib (water faucet) attached near the bottom so you can drain water out when you want to use it. Most people put the container on cement blocks so the hose bib can be placed as near the bottom as possible. You can build your own rain barrel or buy a rain barrel from the River des Peres Watershed Coalition or from various companies. Search “rain barrel” to find directions and suppliers. You’ll want to use the water before the next rain so the barrel will fill again and keep that water from running off into the storm sewer system. You can drain it into a watering can and water plants with it, or attach a hose and let the water drain onto your lawn or into your garden if these are downhill from your barrel. Special soaker hoses that work on low-pressure water from rain barrels are becoming available; check with hardware or garden suppliers.

You can also create a special garden, called a rain garden, to capture all of your roof’s runoff and use it to grow attractive plants that like extra moisture. To make a rain garden, you dig a shallow basin downhill from one of your downspouts and far enough away from your house so the water doesn’t damage your foundation. After you’ve dug the basin, you plant it and mulch it, then attach an extender to your downspout to direct the water into your rain garden. 

Here’s a photo of my rain garden, taken soon after planting it in April 2009. You can see a rain barrel behind the rain garden; the barrel overflows into the garden.

To learn more, request Native Plant Rain Gardens from the Missouri Department of Conservation. Rain Gardening and Storm-Water Management, available from Missouri Botanical Garden, is a more in-depth guide to creating and managing a rain garden. Search “rain garden manual” on the website to find it. You can install a rain barrel under your downspout to collect water for your container plants, then direct overflow water to a rain garden, as I did. Homeowners, apartment complexes, schools, churches, and businesses can install rain barrels or rain gardens. Check out Hazelwood Southeast Middle School’s rain garden sometime!

Coal Bank Road site: Watkins Creek at its best

One of the first sites our Stream Team began monitoring is about where Coal Bank Road crosses over Watkins Creek. This is near where the creek empties into the Mississippi River. We chose this site to monitor for two reasons. The first is to learn about the state of the creek near its end, to get an overall picture of the levels of any contaminants. As I mentioned in the previous post, we are particularly interested in the levels of E. coli and chloride (salt), two pollutants found in Watkins Creek at levels exceeding Missouri state standards. By monitoring near the mouth of the creek, we can see the cumulative effect of these pollutants.

The second reason we monitor at Watkins Creek is because this is one of the easiest sites to walk to along the main stem of the creek (the longest path the creek takes from source to mouth). The photo below shows the west bank at this site, where we walk to the creek.

Notice the gentle slope (for Watkins Creek, at least) from the stream bank up into the riparian corridor. Creeks in watersheds with only small amounts of impervious (hard) surfaces like roads, rooftops, parking lots, and the like exhibit this sort of gentle slope up from the stream bank into the riparian corridor (the area just above the first rise from the stream bank). In such a watershed, rain falls onto absorbent soil and percolates through the soil down to the water table. The water table keeps the stream flowing during dry periods. The soil holds a lot of water during wet periods and what water it can’t hold flows slowly over the ground and eventually enters the creek. When it rains, the water level in the creek rises slowly and goes back down even more slowly. This keeps the velocity of the water rather low and the water level doesn’t vary greatly, thus the stream tends to not erode the surrounding land to a large extent. As long as the impervious surface in the watershed is less than about 10%, the stream will have this sort of gentle slope up from the bank and it will be easy to walk right up to the stream.

Watkins Creek has a much higher level of impervious surface in its watershed than the ideal of 10% or less. Overall the impervious surface is probably closer to 25% (I cannot find the exact number as I am writing but this is about right). Looking at a map of the watershed, the impervious surface is unequally distributed; a higher proportion of the hard surfaces are upstream of Lilac Road than downstream. Once the stream crosses Lilac Road, it can spread out a bit and the water velocity slow down somewhat. By no means does it do this enough to be called unimpaired by the time the creek crosses under Coal Bank, but it does slow down enough above Coal Bank that we can access it without using a rope.

Next time I’ll discuss some of the biological and chemical testing that we’ve done at this site and the results that we’ve obtained.