Civil/Structural Engineering, Vashon, Washington, USA 206-463-5311

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Click on our "Landslide Action" button below to learn more  about what you need to do if you've had a landslide.

Landslide Prevention

Prevention (Mitigation) Of Landslides


 Things To Do:

  • Research Your Site – The best method of research is to hire a Geotechnical Engineer to assess your specific site.  There are other resources available, such as soil maps, but none will as effectively with your specific site.
  • Follow The Geotech’s Recommendations – The Geotechnical Engineer will produce a report describing the historic geology of your site, the landslide risks you may face, and recommendations on how to mitigate those risks.  Do what you can afford.
  • Follow Current Laws and Regulations – Observe proper setbacks from the top and toes of slopes, and grade the site to drain away from the slope.
  • Maintain Slope Vegetation – Maintain vegetation on the slope, and encourage the growth of “water-loving” deep-rooted plants.  Remove at-risk trees; an arborist or landscape architect can help.  “At-Risk” trees may include dying or rotted trees, and stand-alone trees that, if they topple, may rip out a large portion of the bank or may threaten a house.
  • Maintain Drainage – Maintain all drainage systems on your site.  These may include ditches, drain pipes, and downspouts.  Keep as much water as possible away from the slope.  


      Things To Not Do:

  • Don’t Add Water Near The Top of The Bluff – Don’t install anything that will provide water to the top of the bluff: no irrigation system, no septic drainfield, no downspout water.
  • Don’t Dump Debris On The Slope – Don’t dump any debris on the slope, including prunings or grass clippings.  These may kill underlying plants that help stabilize the slope, and may contribute to future erosion problems.
  • Don’t Change Natural Drainage Paths – Don’t fill or change natural drainage paths such as swales or seasonal streams.  There is a reason that nature chose those paths; to fill or change them is to invite problems.  In extreme situations, a civil engineer may be able to design alternatives that will still provide proper drainage.
  • Don’t Cut The Toe of a Slope – Cutting into the toe of a slope is one of the surest ways to encourage a future slide.  If a slope toe must be cut, an engineered retaining system should be installed.
  • Don’t Overlook Slide Indicators – Don’t be lulled into complacency because a slope has been stable for 20 years or more.  Watch for soil cracks, water springs on the face of the slope, dying vegetation, tilting trees, and small erosion problems.  All may be warning indicators of a future slide.