garden, retaining walls

We have a sloped area in our backyard. The slope varies from about 20 degres to 40 degrees. We want to develop this area with stairways and flat terraces. There are a number of young birch tres on the slope(15 inch diameter trunks. We want to put some retaining walls and terraces near some of these trees. Can I level the ground around them or will this disturb the roots or kill off the tree, or what? Could I level off the down-slope side of the tree only, leaving the upslope side of the trees undisturbed? I would be interested in your advice.

 

Fifteen inch diameter trunks make these pretty good sized trees. Not knowing your soil type it is a given that the roots cover a fair amount of area. I have seen trees killed by removing roots several feet away from the trunks on one side to put in a driveway and walkway.

To be on the safe side talk to a local nursery that sells trees and ask the professionals there (who are familiar with your soil type) what their recommendation is as to how close you can get to the base of the trees. They will also be able to advise you how much soil it is safe to add in your area over the existing roots. Usually the recommended level is no more than 2"-4" of soil.