When soil gets eroded and ends up in streams, rivers and other waterways, chemicals that exist in soil mix with the water and create problems for plant and animal life. For example, when phosphorus levels get too high in a body of water, they lead to algae blooms that can kill fish populations. The best way to prevent erosion is to keep the soil in place by planting plenty of native trees, shrubs, grasses and groundcover. The plants' roots hold the soil in place and keep it from falling into the water