Extreme Drought + Heavy Rain = Accelerated Erosion?

[DH001]

The reasons you are seeing the pothole like features on the downhill side of roots or small ledges is because water gains energy as it free-falls off of the edge of these features and the angle at which the falling water hits the soil goes directly into dislodging soil particles. If the drop is large enough and the soil weak enough, the water will start to dig a hole as it dissipates energy. When water flows down or across a trail most of the energy is absorbed by the water itself trying to flow around and over things.

I have seen this phenomenon even during non drought conditions so I don't think the drought is the single biggest factor. However, it obviously doesn't make the situation better.