Plants no matter the type or size cannot stabalize a deep seated slope stability problem.  

Properly designed and installed plantings can help with shallow stability problems and very low slopes.  

Ohama:

GeoPaveTraffic hits the nail on the head.  For any slope stability concern, you should really seek to identify the cause(s) of the problem.  Once you know the causes, then you can address the stability.

A local geotechnical engineer should be consulted.

I would not just pick up the phone and call any, I would call a structural design firm or transportation design firm and ask which geotechnical engineers have the best reputation in your area for slope stabilization issues and give them a call.

Glen

GeoPaveTraffic, gandersen, thanks for the replay.
I concur that any possible shallow soil is more likely to be reinforced (by specific species of grasses). With this type of vegetation, I can understand that the vegetated soil behaves like a composite material because the roots are relatively small and heavily distributed over the shallow depth.
However, using different plant (e.g. willow) to reach deeper locations, apparently the previous mechanism might partially still valid or at least the big root may work as a soil’ nail?

While the suggestion that deep seated slides may not be stavbilized by deeplants, depending on the depth of failure, ther is a possibility that plants may work especially if the problem is water related. How often have we noticed cuts that have been stable for years show sloughing after seasons with heavy precipitation. AOne characteristc of such slope is that they are bare of vegetation except grasses.

Yes an investigation needs to be done but for some tupes of failure as those described above ther may be every chance that deep rooted vegetation may work. I have notedthis to occur in forest clearing where conditions after would suggest the installation of deep drains etc as the ater table after deforestation moves closer to the surface. Why was the are astable before is often the question one has to pose.

Robin Sotir has done alot of work in Bioengineering and has published info in text and papers on this subject. You may wish to review some of this info.

There is also a book out - say in last 8 years on bioremediation of slopes - sorry, the title escapes me - but it was promoted heaviliy on those cards that ASCE sends out.  For the most part, I would count on grassing and shrubbing to take care of surficial erosion type movements rather than deep seated ones.  Of course VAD is right, but to get mature trees in and their roots extended - well, it is a natural phenomenae rather than a project oriented (short time frame) one.

BigH:

I think the book you may be referring to is by Gray and Sortir.

Professor Doug Stead at Simon Fraser University BC has published some papers on this subject wrt forestry works.  They are listed on his web page at the university.

Another wack for your horse; Washington State DOE has put out a small manual on bioengineering of slopes for homeowners concerning coastal land management.  You may have different vegetation in the Midwest, but the application would be analagous.  I'll give you the web-version.  I obtained my copy by emailing the WA State DOE and had it   mailed, free of charge.  It's a nice little durable booklet, and I think it's put together a little better than the printout-version.  The publication outlines a few stabilization methods including practicalities like where to shop for plants and amount of manpower needed.

Good luck!


Slope Stabilization and Erosion Control Using Vegetation

http://www.ecy.wa.gov/programs/sea/pubs/93-30/

There was a recent paper published in the Indian Road Congress' Indian Highways in May that discussed this in detail.  I will try to find out if it can be obtained on-line.  If not, let me know your e-mail address and I will scan it and send to you.

Great topic, I was wondering if anyone could comment on using trees to prevent runoff, and subsequent ponding by acting as natural sump pumps. If a tree can consume 500 gallons a day, then a mixture of grasses to slow runoff and a tree to consume could reduce runoff ? BTW does normal lawn grass consume more water than trees?

plants don't consume runoff, they consume subsurface moisture.  The runoff still occurs.  However, you are correct that increased vegetation will slow the runoff and allow more to soak into the ground.

Everything has been pretty well covered here, however I would also add that in general the potential for slope instability increases with added mass.  Hence, if vegetation is able to reduce the amount of water infiltration (increase of mass and decrease of strength) through absorbtion or runoff, the potential for instability may be slightly reduced.
While it is a step in the right direction (vegetation) it should not be considered to 'stabilize' any slope.

There's a paper on this subject in the UK Institute of Civil Engineers "Geotechnical Engineering", October this year - Just out

Slope Stabilization and Erosion Control Using Vegetation

It's available for free on the Washington State DOE website:

http://www.ecy.wa.gov/programs/sea/pubs/93-30/index.html

I also got a pamphlet in the mail, shipped-  free!  I'll make another post if I can remember who I called for that.  

:)