If you have overland flow the soil is well below its water infiltration and retention potential.
Michael Newby wrote:How well vegetated are the hillsides? I would look at ways of slowing and infiltrating the water as high up as feasible then work your way down the property. If the hills are too steep for swales or terraces then you can still plant shrubs and trees on contour which will create a type of swale on contour as the plants collect debris that's making it's way down the hill. .