Ridge up and down increase soil loss.
	Soil loss increases with ridge height up to about eight inches.
	The increase in soil loss begins to decrease as land slope becomes greater than 6% and disappears by a land slope of about 20%.
	Ridge height decays with rainfall and interrill erosion and thus the ridge effect decreases over time.
	Effect ranges from about 1.5 (ridges increase soil loss from unit plot condition) for high ridges to about 0.9 for a flat surface.
	Unit plot is assumed to have some ridge height, which is the reason for the 0.9 value.
	Ridges on the contour reduce soil loss.
	The effect of ridges increasing soil loss decreases as relative row grade decreases.