To repeat, in my area, No permit required for wall under 4 feet. The only setbacks in bylaw apply to distance of buildings from the proprty line( Setback is 4ft on side lot lines). Being on side of a hill, There are many lots here around me where the property lines are stepped with retaining walls. Some are above that 4 ft limit, So if built today, would need permitting. Dont need a permit for concrete or paving either. Can pave the entire lot line to line.
As a side note, There is a local tree protection bylaw. It applies to trees 8" dia at the trunk or greater. In that case, If you are applying for a building permit for whatever, The city makes you come up with a plan to preserve such trees, even if they are not on your property. Example, a short distance from me, There is a large (80 feet high) douglas fir on one lot only a few feet from the property line. Developers on the lot next door had to modify their digging plan to not come within about a 20 foot radius of that tree. Its marked off with a red fence line on their side, "No dig zone"