In the last 6 months the level of the soil in my back yard has dropped 4-6 inches exposing all the sprinkler heads and tree roots. Whats going on?
It could be one or more of several things. First, rain is a main source of erosion. erosion from rain occurs when there is a dry period, drying the soil down several inches. The rain then lands on the dust, splashing mud and dust and traveling downhill as the amount accumulates. When rain erosion removes a layer of topsoil, there should be a level area on the uphill side of roots or large rocks where the mud pooled on its way downhill, and drained. Second, If your soil was very dry and dusty, wind can quickly move large amounts of topsoil. The result usually looks like the ground is sunken between roots and rocks, and where there are no healthy root systems. Third, soil compaction can put moist soil down several inches in a relatively short amount of time.
Here are some good tips to reduce soil erosion: