Testing has shown that a 3-4 inch layer of barkdust will outperform straw, erosion fences and hydro mulch for erosion control. When applied to exposed soil of hillsides, the fibers act as millions of tiny sponges holding back the free flow of water carrying sediment and silt. The surface of the bark deflects the energy of rain drops while the mulch itself absorbs the water and then slowly releases it. Bark mulch also controls erosion on new construction and may later be tilled in as a soil amendment, reducing the amount of material that will have to be purchased and applied during final landscaping.