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Stormwater Management
Stormwater Improvement Projects

Click here to see dramatic results from Johnston's recent stormwater improvement projects that took place throughout the city.  The video explains why the projects are needed, where taxpayer dollars are going, and what will be the final result.   Visit the stormwater projects page to your left to learn more about each individual project.

What is stormwater?


Stormwater runoff is the rainfall or snowmelt that runs off surfaces like roads, buildings, sidewalks or compacted ground surfaces. As the City of Johnston has grown, more and more precipitation has become runoff. Now it is estimated that 30–50% of the precipitation in Johnston is runoff.

As communities grow, they often experience more stormwater runoff problems due to the increase in areas that don't absorb stormwater. Rainfall and snowmelt that would normally infiltrate into the soil becomes runoff. This increases both the volume and rate of runoff, which leads to flooding, streambank erosion, and potential damages to public and private property and water quality.

Stormwater can flow directly to streams and lakes or it may be transported by municipal storm drain systems. Unlike sanitary sewers, storm sewers do not lead to treatment plants, but drain directly into our streams and lakes.

In a normal year, 90% of the rain events in central Iowa bring 1.25 inches of rain or less. The City’s goal is to absorb as much of this rainfall on the land as possible, so we can significantly reduce erosion and flash flooding and improve the quality of water in our community.

Why is Johnston concerned about stormwater runoff?

Along with other pollutants, Beaver Creek, which flows through Johnston, is impaired by E. coli bacteria. After flowing thorough Johnston, Beaver Creek enters the Des Moines River (a drinking water source) which is impaired by E. coli bacteria and nitrates. Both are also polluted by topsoil (sediment).

For more information on stream impairments, contact the Iowa Department of Natural Resources or go to the US Environmental Protection Agency website.

What is the City of Johnston doing about Stormwater Management?


In May 2004, the City of Johnston became an “MS4 City” with a Municipal Separate Storm Sewer System permit issued by the Iowa Department of Natural Resources. This permit regulates the City’s requirements for managing stormwater. 

Click here to see a copy of Johnston’s current MS4 permit.

In 2009, Johnston completed a Watershed Assessment and Stormwater Management Plan with priorities and recommendations.

The City Council approved ordinances to regulate illicit discharges, erosion and sediment control and stormwater management. Click here for a copy of the Municipal Code.

The City Council also approved a Stormwater Utility, specifically to address water quality (pollutants) and water quantity (flooding). For more information, click here.

The City conducts water quality sampling at 10 sites around the community three times per year, a summary of those samples can be found here.

What can I do to Prevent Water Pollution?

There are a number of practices homeowners can use on their properties to limit their impact on stormwater runoff and quality.  A detailed toolbox of techniques and practices, as well as a list of contractors trained to do the work is available on the Rainscaping Iowa website.

Also, the following is a list of practices you can begin today to help become part of the solution to preventing water pollution:

Home Maintenance

• Buy household products such as cleaners and furniture polish labeled "non toxic." Use small quantities and purchase only the amount you need.
• Properly use and store all toxic products, including cleaners, solvents and paints. Use up paint cleaners and other products or share leftovers with a neighbor.
• Take household hazardous materials and containers to a hazardous material collection center.
• Use kitty litter or other absorbent materials to clean spills. Depending on the substance, dispose absorbents in the trash can or at a hazardous materials collection center.
• Rinse water-based paint brushes in the sink. Filter and reuse paint thinner or brush cleaners. Dispose of used thinner, oil and latex paint at a hazardous materials collection center.
• Recycle reusable materials. Throw litter into trash cans and keep cans tightly covered to prevent foraging by animals.
• Control erosion during construction to prevent dirt and debris from entering storm drains.

Lawn and Garden

• Use pesticides, herbicides and fertilizers in accordance with label instructions. Do not apply before rain, or during strong winds, and dispose leftovers at a hazardous materials collection center.
• Use a broom rather than a hose to clean up garden clippings. Put leaves and clippings in a separate yard waste cart or a compost pile.
• Divert rain spouts and garden hoses from paved surfaces onto grass to allow water to filter through the soil. Water only your lawn and garden.
• Pick up animal waste and dispose in the trash can.

Do you have a stormwater concern? For example, is there mud in the street, or have you witnessed a spill or dumping in the storm sewer? Do you have a question about a program or an issue?

Please go to the Iowa Stormwater Website and click on “Report A Stormwater Concern.” A Johnston city staff member will be in contact with you.