Open ditch construction for roadside drainage shall be permitted in low density areas, and constructed according to Ohio Department of Transportation specifications. Minimum depth of ditches shall be two (2) feet below the edge of pavement, and one (1) foot minimum at top of hill and toe of bank. All ditches shall be protected against erosion. Curlex or approved equal shall be used in ditches up to 2.5%. Sod or Rip-Rap shall be used in the bottom and sides of ditches up to 5%, and tile or paved gutters shall be used in ditches over 5%.