A river corridor can be viewed as a hierarchical series of river segments, from upstream headwater streams to large downstream rivers. River corridors include the river channels and the river margins (the water-land interfaces), and both are influenced by surface water-groundwater interactions. These environments are characterized by hydrological, geomorpho-logical, environmental, and ecological interactions. River margin interactions influence surrounding terrestrial landscapes.
Features that influence the structure and functioning of river systems occur at various spatial scales. A stream or river, for example, has an input-output relationship with the next higher scale, the stream or river corridor. This corridor scale, in turn, interacts with the landscape scale, and so on up the hierarchy. Similarly, because each larger-scale system contains the smaller-scale ones, the structure and functions of the smaller systems affect the structure and functions of the larger. Investigating relationships between structure and scale is a key first step for planning and designing stream or river system management plans.
Landscape ecologists use four basic terms to define spatial structure at a particular scale. These matrix, patch, corridor, and mosaic spatial landscape component types in river basins are illustrated in Figure 2.
The watershed scale that includes the stream corridor is a common scale of management, since many functions of the stream corridor are closely tied to drainage patterns. While the watershed scale is often the focus of river restoration and water resources management, especially for nonpoint pollutant discharge management, the other spatial scales should also be considered when developing a stream or river system management policy or plan. The exclusive use of watersheds for the large-scale management of stream corridors, however, ignores the materials, energy, and organisms that move across and through landscapes independent of water drainage. A more complete large-scale perspective of the stream and river system management is achieved when watershed hydrology is combined with landscape ecology and when actions in problem-sheds rather than only in drainage basins are considered.
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