Although many riparian areas can be restored and managed to provide many of their natural functions, they are not immune to the effects of poor management in adjacent uplands. Upslope management can significantly alter the magnitude and timing of overland flow, the production of sediment, and the quality of water arriving at a downslope riparian area, thereby influencing the capability of riparian areas to fully function. Therefore, upslope practices contributing to riparian degradation must be addressed if riparian areas are to be improved. In other words, riparian area management must be a component of good watershed management.
Riparian areas have received variable levels of attention depending on the field of inquiry. For over 100 years, the term “riparian” has been closely associated with water law. A “riparian” water right generally provides a landowner whose property borders a stream, river, or other body of water the right to use a portion of that water for various purposes. Recognition of the term “riparian” in the basic sciences has been much more recent; since 1970 there has been an explosion of information addressing ecological, hydrologic, biogeochemical, aesthetic, cultural, and social topics related to riparian areas.
Because of the relative newness of our understanding of how riparian areas function, a single precise ecological definition of the term has not yet emerged. However, most scientific definitions of “riparian” share common features, including mention of location in the landscape, hydrology, and sometimes vegetation and soil type. Because the lack of a consistent definition has been identified as a major problem of federal and state programs that might manage and protect these areas, the NRC committee developed the following definition.
Riparian areas are transitional between terrestrial and aquatic ecosystems and are distinguished by gradients in biophysical conditions, ecological processes, and biota. They are areas through which surface and subsurface hydrology connect waterbodies with their adjacent uplands. They include those portions of terrestrial ecosystems that significantly influence exchanges of energy and matter with aquatic ecosystems (i.e., a zone of influence). Riparian areas are adjacent to perennial, intermittent, and ephemeral streams, lakes, and estuarine-marine shorelines.
An important feature of this definition is the concept of riparian areas having gradients in environmental conditions and in functions between uplands and aquatic ecosystems. The shaded zone of influence in Figure ES-1 represents this gradient. Although riparian areas encompass some of the wetlands in a typical landscape setting and also include portions of adjacent aquatic and upland environments, important distinctions between these systems are made (Chapter 1).