need a pic...

otherwise.. time to get rid of them.. or rebuild the wall ..

else they will have the potential to fall over.. if you remove significant root mass.. on a dangling cliff.. dont you think. ...

ken

One problem with pruning crApe myrtle roots (in addition to the normal drawbacks of such a practice), is that crApes frequently sprout back up from root pieces left in the ground. So, the plant will try to grow a new plant just about everywhere you cut a root.

BTW, it is very likely that the excess watering has contributed to the surface roots. Crape myrtles don't need much water and their roots will grow preferentially near the surface where they can't get sufficient gas exchange at lower soil levels.