According to the Brooklyn Botanical Gardens, more than 3 billion tons of topsoil are lost to soil erosion and mismanagement. Topsoil is the top layer of soil, between 2 and 10 inches deep, that provides the nutrients and medium for plants to grow. A topsoil's quality is determined by its composition, pH, texture and salinity. Erosion can cause any of the qualities to be severely compromised, and may remove top soil from your area altogether, revealing the inferior subsurface layers.
Mulch the soil during the summer and late fall to retain moisture in the topsoil and prevent it turning to dust, which is easily blown away. The Brooklyn Botanical Garden recommends never using a leaf blower, as it may blow away dry topsoil.
Plant cover crops for the winter, such as rye grass and alfalfa, to prevent winter snow and rains from removing top soil from the area.
Place trees around gardening areas to break the strength of wind, preventing dry topsoil from blowing away in the breeze.
Till the soil in the spring, not the winter, to prevent topsoil from washing away during winter snow and rains. Purdue University's website recommends leaving crop debris in the soil as it protects top soil from rain.