posted 8 years ago
If I am understanding correctly, you have an existing stream and then another erosive runnel - I'm assuming it is running into the stream? If I am understanding correctly, this sounds to me like a situation that needs to be addressed with plantings and possibly swales on contour. The trick to managing erosive water flow is not to capture it where it is eroding the land, but to divert it, spread, slow and soak it Before it gets to that point.
Once the water concentrates it is pretty much too late to try and prevent the erosive action.