There has been very heavy rainfall not only recently but on and off for weeks. This has created some severe erosion of the bare slopes around the pond of which this section is the worst.
I feel like we should have documented this as a geology lesson in fast-forward. It started with a trickle across the path, which quickly deepened into a mini-ravine. The gravel got washed down the slope and fanned out into the pond - just like the illustrations in our geology textbooks - or like the Mississippi delta!