Timber harvesting is allowed in the SMZ, providing the objectives of the SMZ are not compromised. SMZs provide a water filtration strip of groundcover on ephemeral areas.

An effective SMZ provides an adequate canopy of forest cover along all perennial streams to maintain normal water and shade conditions. An effective SMZ minimizes forest soil erosion by maintaining the appropriate amount of residual ground cover under various soil and slope conditions. Note the number of wing ditches on the haul road.