Typo correction, was supposed to read

"i.e. this is not originating with surface erosion"

The erosion occurs in a mid-layer of the exposed bank.
Removing water at the surface is also a concern.

-jay

Most bamboo's grow w/in the first 2 feet of soil, but if you get a large runner (is there a height restriction?) it will spread a mat over a large area (ok, so will some of the smaller ones, but i would think the larger ones have a deeper root structure). There are lots of good areas to buy from in Washington. I am thinking that Vivax or yellow grove would work well as they are fairly invasive in washington... Phyllostachys aureosulcata 'Spectabilis' would look great on a bank but I don't know if it's as invasive as yellow grove.

Thanks for the info. Could someone provide economical sources to purchase vivax, yellow grove or bissiti? Also, would these be evergreen in western WA?

-jay

bambu-u.com
bamboogarden.com
Ordered from both of them. Happy with product.
I would assume with your pleasant location, You could visit some bamboo nurseries in your region.
Will they be evergreen?
I presume they would be, but kudzu and others might have a better knowledge of that. Also, sometimes bamboo can get windburn even in moderately warm climates.

Don't buy seedlings, find somebody with a mature grove they want to get rid of..

Just watch out for bamboo mites in the nw bamboo forests. Supposedly, they are common there.