Customer has a retaining wall on a hill to provide space for inground pool. At the bottom of the wall there is a ledge about 2ft. wide tapreing to 1ft. then it dops down a steep slope of bare dirt. At the bottom is swale to prevent run-off from going to the neighbor whose house sits lower. Any ideas on preventing the slope from washing away? Since it faces away from the backyard they aren't too concerned about looks but it is visible as you drive up to the house (end of cul-de-sac).