EROSION CONTROL, CAMEROON. Mount Oku, Bamenda Highlands. Establishing a contour hedge to prevent erosion. The A-frame is used to plot a level contour across the slope Initially, Tephrosia, a leguminous shrub is sown followed by Calliandra, an exotic tree species. Contour hedges help prevent soil loss from steep slopes, thus reducing the need to destroy more of the forest.