mini retaining wall

[Mr T]

I am building a small retaining wall out of landscaping timbers (treated 3x4 with rounded sides). It will be a foot tall (4 timbers high). It is for around a crawlspace enterance, bordered 2 sides by flower bed, 1 side by yard.

Should I put gravel behind this for drainage/mud control, or is it not needed for a wall of this height? There is overhang from the house covering about 18" of the wall (comes out 4.5 feet.)

[xkvator]

some gravel up against might make the landscape ties last longer, as you won't have damp dirt against them.