Or. Admin. R. 808-002-0872
Landscape "retaining walls" as used in ORS 671 and this chapter is a structure designed to a height exceeding six (6) inches from the lowest finish grade and constructed to resist the lateral pressure of soil, when there is an actual, or desired change in ground elevation that exceeds the angle of repose of the soil.
ORS 671.760 & ORS 670.310
ORS 671.520 & ORS 671.540