Johnson County Soil and Water Conservation District

Best Management Practices

Best Management Practices (BMP's) are simple techniques that improve water quality and reduce the quantity of water that runs off your property.

Driveway and Parking

Curb Cut- Retrofitting

  • Allows runoff to bypass the storm sewer. A great way to introduce stormwater management into an existing commercial parking space

Permeable Paving

  • New concrete, asphalt, and paver block technologies reduce the need to find locations to intercept runoff.



  • Annual core aeration improves infiltration, and fertilizer penetration.
  • Perform prior to a compost application to improve your soil organic matter content.


  • For new construction, consider applying 2 inches of composted organic matter.
  • Try to increase your soils organic matter to 5% (measured with your soil test)
  • Grass will retain more water, need less fertilizer and do better in dry summer months.


  • Mow to 2" height during cool weather
  • Mow 3" during high temps not clipping off more than 1/3 of the leaf height.
  • Not bagging clippings provides up to 75% of your annual fertilization needs and increases soil organic matter

Landscape Management

  • Bioretention “cells” are shallow depressions filled with amended soil mix, topped with a  layer of mulch, and planted with dense vegetation. Storm water runoff flows into the cell and slowly percolates through the soil (which acts as a filter) and into the groundwater; some of the water is also taken up by the plants. Bioretention areas are usually designed to allow ponded water 6-8 inches deep, with an overflow outlet to prevent flooding during heavy storms.


  • A  bioswale is nature used as technology. They are storm water runoff conveyance systems that provide an alternative to storm sewers.  They can absorb low flows or carry runoff from heavy rains.  They improve water quality by infiltrating the first flush of storm water and filtering the large storm events.

Native Vegetation

  • Native grass/flower (prairie) plants can help restore and enhance soil quality and improve storm water infiltration rates. These species will survive both wet and droughty periods.

Rain Garden

  • A rain garden  is a shallow depression that typically collects water from impervious surfaces such as roofs and allows plants, bacteria, and soil to filter the water.
  • Designed not to hold water for more than 12-24 hours.
  • It is as simple as digging or locating  a shallow depression where water collects in your yard and planting with perennials. Installation Guide (includes site prep. and plant types)

Downspout Management

  • Change the direction of your downspout.  If downspouts are draining directly onto a sidewalk or driveway, can they be re-directed to the lawn?
  • "French" Drains: Must be kept away from foundations and above the water table
  • Rain Barrels: A great way to conserve water for watering flower/vegetable gardens. Downspouts should be screened to bypass large storms.
  • Soak A-Way Pits/Dry Wells: Designed to receive runoff from individual roof leaders. They are small excavated pits, backfilled with rock.


Water Management Design Resources

Use these resources to design water management features in your landscape.

Iowa Storm Water Management Manual


Iowa Rain Garden and Design and Installation Manual


Iowa Statewide Urban Design and Specifications


Johnson County Stormwater Ordinance

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