Several years ago we piled brush over head high in this erosion ditch. It is filling in the ditch as the brush catches leaves and dirt filters in and stays. Sometimes the rain is so hard that it washes the whole pile of brush, but it all gets caught somewhere and fills in behind it.
This area has filled in pretty well. We have a lot of places like this. It looks pretty messy, but it is doing what I read it would in the Permaculture book.