How to Keep Culverts From Stopping Up

Written by evelyn fielding
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How to Keep Culverts From Stopping Up
Culverts keep water flowing smoothly. (creek image by M. Elizabeth Huetter from

It's important to keep culverts from stopping up through proper construction and maintenance. Clogged culverts impede drainage and may cause flash floods during heavy rains. An improperly draining culvert may also contribute to erosion and road washout, which are far more expensive to fix than simply maintaining the culvert.

Skill level:

Things you need

  • Shovels for small jobs
  • Small backhoe or other digging machine for larger jobs
  • Landscaping fabric
  • Stones or riprap
  • Culvert grates

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  1. 1

    Clean the silt and fine sand from inside the culvert. It's important to reach as far in as possible to remove obstructions in the centre. Dispose of debris well away from the culvert inlet to prevent redepositing of materials.

  2. 2

    Dig all vegetation and a layer of soil away from the culvert inlet in a six- to eight-foot area. Dig out the sides of the ditch if needed. Bring the soil line slightly below culvert grade and gradually taper down into the ditch.

  3. 3

    Install high-quality landscaping fabric. Spread the fabric up the sides of the ditch and away from the inlet about six feet. Landscaping fabric keeps vegetation down and helps the soil hold its structure during heavy rains.

  4. 4

    Install a properly sized culvert grate to keep out large debris, children and animals. Follow local Department of Transportation guidelines for your specific situation.

  5. 5

    Pile stones or large riprap around culvert inlets, below the drainage grade and on top of landscaping fabric up the sides of the ditch. Use golf ball-sized stones and larger. This also helps keep vegetation down and protects the fabric from excessive sun damage.

  6. 6

    Check culverts frequently and clean them as needed. During rainy seasons, check at least monthly or after a particularly heavy rain. Check during dry seasons as well to make sure animals have not moved in and plants are cut back.

  7. 7

    Keep ditch and inlet areas properly mowed.

Tips and warnings

  • Small culverts clog more easily. The minimum diameter should be 12 inches, and larger diameters are better depending on your situation.
  • Frequently clogged culverts are a symptom of poor drainage. Improve the whole drainage system as needed to allow clear flow of water.

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