Understanding stormwater
On the trail of runoff:
Where stormwater goes and why it matters
Why should you care where stormwater comes from and where it ends up? Because not only are storm sewer systems efficient at conveying stormwater from streets, parking lots, and other low areas to prevent flooding and keep roadways safe for travel, they’re also great at transporting runoff that contains pollutants. Sediment, excess nutrients, chemicals, yard waste, and pet waste can fill water resources, impair water clarity, promote weed and algal growth, and harm aquatic plants and animals. While stormwater (water from rain and snowmelt) has always existed, the amount of stormwater runoff (water that flows across the land surface) in Minnetonka has increased significantly as the land was developed, creating more impervious surfaces—hard surface areas that prevent water from absorbing into the ground.
Help reduce runoff as well as keep our waters clean by learning more about runoff and following some of the brief tips listed below.
- Rain that falls on buildings generally flows quickly off the rooftop to the ground or into a gutter and downspout system intended to direct water away from the foundation.
- Directing downspouts toward your lawn, trees, shrubs, or other vegetation, rather than down your driveway, can help reduce stormwater runoff by slowing the water and allowing it to be absorbed into the soil. Avoid redirecting runoff towards adjacent properties or your home.
- Runoff from paved surfaces will carry with it any chemicals or other materials left on the surface such as soil, loose gravel, sand, radiator fluid, fertilizer, grass clippings and pet waste. Keep paved surfaces clean and vehicles maintained to prevent leaks and materials from washing into the street. Avoid applying fertilizers and herbicides to your lawn just before it rains.
- Roadways often serve as collection points for stormwater runoff, so avoid blowing grass clippings and leaves into the street. Any material that washes into the street is passed downstream.
- Catch basins support the metal storm grates in roadways and drain water from the pavement while allowing traffic to pass overhead. Catch basins typically are connected to large pipes below the ground. Removing accumulated debris such as trash, leaves, and twigs from around the catch basin grates can help prevent flooding and keeps these materials out of the storm sewer.
- The individual networks of pipes and structures (such as catch basins) that capture and convey stormwater is the storm sewer system. Most people only see very small portions of storm sewer systems, such the storm grates, access covers, and culvert ends, as much of the system is underground.
- Most storm sewer systems discharge directly to the nearest lake, creek, or wetland. Unlike sanitary sewers, the water in storm sewers is not treated before it is discharged, because storm sewer systems are intended to carry stormwater (rainwater and snow melt), not septic or other waste materials.
Some neighborhoods may not have underground storm sewer systems at all. Instead, water is directed along the surface through drainage channels or along the roadway itself, while some newer developments may use drainage ponds or infiltration basins (rain gardens) to help lessen the effects of increased stormwater before discharging it into a lake, creek or wetland.
You don’t need to wait until it rains to figure out where the stormwater goes on your property—just remember that water flows downhill. See if you can determine where the stormwater goes in your neighborhood.
