Civil/Structural Engineering, Vashon, Washington, USA 206-463-5311
Ellisport Engineering Blog
Correcting an Omission

I felt a little silly when speaking with a potential landslide client recently.  We’ve done a pretty good job of talking about landslides on our website.  But I also wanted him to refer to our information on recommended plantings for sloped sites.  And that’s when I realized that I didn’t have any of that information on our website.  I forgot to post the planting information!

 

Over the years, I’ve accumulated a variety of documents from mostly government sources that list plants which are recommended for steep slopes.  These plants are intended to help stabilize the upper soils of the slope by their deep roots, by extracting water from the soil, and by shedding water off their leaves down the slope.  The documents list pros and cons of the plants, types of soils, steepness of slope, and availability of light.  Hopefully, you’ll find these documents helpful.  If you have questions, please feel free to call us.  If I can’t answer them, we also have a landscape architect on staff who can help.

 

Also, remember the Big Three Things that are primary considerations with slope stability:

1. Ensure toe stability, either through toe soils at a proper angle of repose, or through mechanical means such as a wall or rockery

2. Encourage plant growth on the hill to stabilize the upper soils with roots and mitigate erosion 

3. Collect and control all drainage at the top of the hill, and locally collect water from hillside springs.  The water should be piped to a proper disposal site at the toe of the slope (drainage ditch, catch basin, storm sewer, or onto the beach).

 

If you can assure that all three conditions are met with your slope, it will likely perform much better in our extreme rainy season, both short-term and long-term.

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