Abstract: A matting, anchored to the ground surface of an enbankment adjacent a body of water for preventing erosion of said ground surface due to action of said water thereon, is so constructed that it provides less resistance to the flow of water therethrough in the direction from the ground surface toward the body of water than it does in the opposite direction from the body of water toward the ground surface. The preferential flow characteristic can be accomplished by providing the uppermost layer of the matting, facing the body of water, with a plurality of holes that are selectively covered by pressure responsive flaps. In the alternative, the preferential flow characteristic can be accomplished by providing the matting with plural layers of different fiber thickness and different pore spaces, with the uppermost layer of the matting having fibers of finest thickness and least pore spaces, and with the fiber thickness and pore spaces in the matting each increasing toward the base or ground side of the matting.