Sediment, nitrates, phosphates, and thermal pollutants are effectively reduced by riparian areas. Riparian forests can also effectively remove nitrates from ground water. Eroded materials and attached pollutants from upslope areas are trapped on the surface. Riparian forest water quality functions have primarily been studied on cropland watersheds where slope has not been a factor. While sheet flow is not required for effective removal of NPS pollution from runoff passing through a riparian area, concentrated flows must be dispersed before upland runoff enters the riparian area.
Nonleguminous hardwoods are the most effective vegetation for nitrate removal.
Where shade is critical, taller conifers may be preferred. The vegetation should be managed to retain larger trees near streams and denser, more vigorous trees on the remainder of the area. Plan restoration as part of naturally occurring aquatic ecosystems. States should factor in ecological principles when selecting sites and designing restoration. These sites are likely to be more suitable for restoration if the original hydrology has not been permanently altered.