Taking the Dirty Out of Stormwater
After the first few rains, our Sonoma County landscape transforms from parched golden brown to rich hues that host a world of vibrant new growth. A celebration is not only warranted for us seeing all this glorious new growth but also creating distance through time from another record setting drought. Water reservoirs this year have been full even before the beginning of our rainy season, and help us usher in the cool green of winter and reassure us there will be more time for wonderment before the risk of another wildfire season creeps in.
As we notice the abundance of stormwater filling the creeks and rivers and appreciate the beauty we are immersed in, we don’t typically delight in the thought of stormwater or the infrastructure that is needed to treat or hold it so that we have less flooding and clean healthy water pulsing through these precious local waterways.
What is the meaning of stormwater infrastructure to you? Does it bring to mind giant unseen concrete pipes, outfalls flowing under roadways dropping turbid water into nearby creeks? Does it look like uninhabitable surface water, or just plain dirty runoff?
What is Stormwater
Stormwater essentially is water that flows over impervious surfaces during a rain event. Typically, it does not easily soak into the ground but rushes off our urban hardscape such as rooftops, parking lots and paved roads. It moves with such force that oftentimes it picks up and conveys pollutants like trash, chemicals, leaves, oil, and fine sediment which all have the potential to harm our waterways and the wildlife that depend on healthy water quality as their habitat.
Stormwater Meets LID
Stormwater infrastructure is not just the typical concrete pipes, outfalls and storm drains seen around towns and cities. This infrastructure has developed over time into an integrated and even attractive part of our urban landscape. You may often pass by a stormwater feature and think it is just landscaping. These features, known as Low Impact Development (LID) treat stormwater but blend in with the natural landscape.
Since its inception, in the mid-1980s, LID has become much more than just detention ponds. In 2005, Low Impact Development emerged in Sonoma County when rain gardens and rainwater harvesting began infiltrating residential areas. The catchy phrase that encouraged the use of these systems, hearkens back to the early 2000’s when water saving partnerships encouraged us to Slow It, Spread It, Sink It. This reference to stormwater was our first taste of LID and how to manage stormwater in our urban environment.
LID Throughout the Watershed
Now LID, which was created to develop more sustainable methods for managing and treating stormwater for growing urban areas, is required for any development that creates or replaces an impermeable surface over 10,000 square feet. As the Russian River Watershed continues to grow and develop, we encounter the requirement for more Low Impact Development features.
Some newer and more common LID features we see in big development areas like shopping centers and high-density housing developments are Roadside Bioretention, Porous Pavement and Vegetated Swales. Let’s take a closer look into these so you may be able to identify them while you are out and about.
Roadside Bioretention and Porous Concrete
Roadside Bioretention often looks like a planter strip between the sidewalk and curb and gutter of a street or in a median of a parking lot. However, when you see a bioretention feature, there is always a way for stormwater to enter the feature. Sometimes a Roadside Bioretention feature has an opening in the curb which slopes into the feature and has cobble at the entrance of the otherwise vegetated area. The cobble dissipates the velocity of the water and allows it to slow before entering the feature. Cobble also captures larger contaminants like trash or leaves from compacting the soils of the feature. A narrow strip of porous concrete along the gutter pan of the road next to the feature can also be the entry point. The water that flows off the pavement spreads and infiltrates in the permeable area of the concrete. As it permeates through the concrete it flows subsurface to the feature and interacts with the soils and roots to treat potential contaminants.
The vegetation and soils in this area are engineered and play an important role in treating pollution. These specialized soils work together with plant roots to bind with the array of pollutants they encounter. As they infiltrate into the ground, contaminants magnetize to the soil and are taken up by the roots of the plants, thereby filtering the stormwater and freeing it of contamination before it enters the stormwater pipes below the surface. Once this water infiltrates through the feature it enters stormwater pipes to get carried to a nearby outfall or waterway.
Vegetated Swales
Vegetated swales or rain gardens are another common type of LID found throughout the watershed. These consist of a built-in depression where water enters the feature from rooftop downspouts, parking lots or roadways. As the water spreads across the vegetated basin, it interacts with the soils and plants in a similar way. As with all LID, these swales are designed to mimic the natural landscape. Water can pond in them but is meant to infiltrate within 72 hours of the rain event. In swales and most LID, during large rain events, there is a high flow drain that can move water more readily into the storm drain system to prevent localized flooding. Since vegetated swales may hold water, it is important that they are planted with appropriate vegetation that can thrive in various conditions. There are zones where the plants need to survive under water for a short time but other zones which do not have such intense water requirements.
Stormwater throughout the Russian River falls to the waterways with no other treatment which is why it is so important to be able to identify and maintain these specialized LID features in our watershed. If you live in a housing development that was built after 2005 you may very likely see LID in the areas around the development. Property owners are required to maintain these features so take note and be sure they are being maintained if you have one on your property.
LID and stormwater infrastructure, like most all water infrastructure, goes unnoticed to the public and is usually taken for granted. We typically only think of this essential infrastructure when we need it most, during intense rain events. As you get outside this holiday season, whether in a parking lot gathering supplies for your upcoming celebrations or out at the nearest newly developed park with loved ones, take a moment to notice the stormwater infrastructure that might be around you. Capturing all that stormwater is a fantastic feat of human ingenuity, and those LID features are magnificent as well. What other infrastructure can you think of that treats pollution before it enters the stormwater system while looking like a green space, fitting into the natural landscape like a gnome hiding in the garden?
An effective and promising approach to curbing runoff pollution involves implementing Low Impact Development (LID) features, aimed at slowing and absorbing polluted runoff. Strategies include:
Why is it important to keep yard waste out of creeks, waterways, and storm drains? 
What can you do to keep our creeks clean?
Soldier Beetles – The first to appear is the solder beetle. Soldier beetles are about ½” long, are commonly reddish orange with dark brown or black wings and are related to the firefly but lack the light producing organ. They enjoy flower nectar and pollen as well as eating soft-bodied insects, such as aphids and small caterpillars. Not only are Soldier beetle great predators, but they also help pollinate garden flowers as they travel among them. Large populations of Soldier Beetles are commonly seen cruising throughout plum trees in the early spring, since the new flush of spring growth on the plum trees are often favored by aphids. Unfortunately, the Soldier Beetles are often misidentified then targeted as the pest and eliminated by insecticides.
Ladybug Beetles – It is always a treat to see the first Ladybug Beetles of the season. They are the star of the beneficial insects. Ladybugs are known to consume a wide variety of garden pests, such as aphids, asparagus beetle larvae, whitefly nymphs, mealybugs, and spider mites, eating upwards of 5000 during their lifespan. There are about 11 species of ladybugs that live in California, over 450 species throughout North America and vairy in color from red, orange, or grey with black spots, and black with two red spots just to list a few.
The ladybug larvae look like a tiny alligator, vary in color as the adult do, will feed on aphids and other soft-bodied pests, consuming hundreds during its 2–4-week larval stage before pupating, emerging a few days later as the adult ladybug beetle. Unlike the adult, the ladybug larvae are not as well-known and often targeted as the pest.
Syrphid Fly – Though it’s hard to pick a favorite, if I had to, the Syrphid Fly would be my pick. Also known as Hover Fly or Flower Fly, these garden allies are not a bee or a wasp though they have stripes. They do not sting or bite, nor will they swarm. As their common name suggests, they ‘hover’ above flowers. They enjoy the nectar and pollen making them an important pollinator. They’re rather small, ranging from 1/8” to ¾” depending on the species.
Syrphid fly larvae are legless and worm-like shaped, will vary in color from pale green to khaki-tan, all with a distinct stripe down it’s back. Larvae will vary in length from 1/32” to ½” depending on their species and developmental stage. These larvae provide a tremendous service eating hundreds of pest insects as they prey on aphids, scale insects, thrips, spider mites, and mealybugs during their 2-4 weeks before pupating.
