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Changes to hydrology, geochemistry, substrate, or species composition may impair the ability of a wetland or riparian area to function properly. Such alterations can affect the ability of the wetland or riparian area to act as a filter for excess sedimentation and nutrients, which can result in deteriorated surface water quality. The following are examples of typical activities that often cause such impairment: the drainage of wetlands for additional cropland, overgrazing, construction of highways, channelization of an adjoining waterway, deposition of dredged material, and excavation for ports and marinas.
THE PROTECTION OF WETLANDS AND RIPARIAN AREAS -- The purpose of this management measure is to maintain the water quality benefits of wetlands and riparian areas and to ensure that they do not in turn become a source of nonpoint pollution due to degradation. Wetlands and riparian zones reduce nonpoint source pollution by filtering out of solution NPS-related contaminants such as phosphorus and nitrogen. The ability of wetlands and riparian zones to perform this function is determined by the vegetative composition, geochemistry, and faunal species composition. Any changes to these characteristics could affect filtering capacities.
THE RESTORATION OF WETLANDS AND RIPARIAN AREAS -- This measure promotes the restoration of preexisting wetland and riparian areas where the restoration of such systems will have a significant nonpoint source pollution abatement unction. This measure is intended to address the increase in pollutant loadings that can result from degradation or destruction of wetlands and riparian areas. These areas are effective in removing several pollutants from stormwater, such as sediment, nitrogen, and phosphorus. Wetland and riparian areas also help to attenuate flows from higher-than-average storm events, thereby protecting downstream areas from impacts such as channel scour, streambank erosion, and fluctuations in temperature and chemical characteristics. This can be accomplished by reestablishing previous hydrologic dynamics, vegetation, and structural characteristics.
ENGINEERED VEGETATED TREATMENT SYSTEMS -- The purpose of vegetated filter strips is to remove sediment and other pollutants from runoff and wastewater by filtration, deposition, infiltration, absorption, adsorption, decomposition, and volatilization, thereby reducing the amount of pollution entering adjacent waterbodies. The ability of a wetland to act as a sink for phosphorus and the ability to convert nitrate to nitrogen gas through denitrification are two examples of the important NPS pollution abatement functions performed by constructed wetlands. This measure promotes the development of artificial wetlands or vegetated treatment systems where these systems will serve a nonpoint source pollution abatement function.