Physiography of Flowing Water - Freshwater Ecology: Concepts and Environmental Applications - page 69

5 Physiography
of Flowing
Water
Characterization of Streams
Stream Flow and Geology
Movement of Materials by Rivers and Streams
Summary
Questions for Thought
Rivers and streams are central to life. Small streams are dominant in-
terfaces between all other aquatic habitats and the land. Streams and rivers
move materials from land to sea through lakes and estuaries, forming a vi-
tal link in global biogeochemistry. Streams and rivers have been well char-
acterized by hydrologists because of interest in flooding, erosion, and wa-
ter supply (for a basic description of river geology and hydrology, see
Leopold, 1994; for practical aspects of special interest to ecologists, see
Gordon et al., 1992). To comprehend the importance of streams in aquatic
ecology, it is necessary to understand their physical geology. In this chap-
ter, I discuss ways to describe streams, characteristics of stream flow, geol-
ogy, and how streams move materials.
CHARACTERIZATION OF STREAMS
First I, describe characterization by watershed features, such as dis-
charge, number of upstream branches, and area. Then I describe how
streams are classified with respect to water velocity and changes in dis-
charge. Finally, classification by vegetation in the watershed is explored.
One way to characterize a stream is by the size of its watershed. As
used in North America, the term watershed means the entire land area
or basin above a specific point on a stream where water flows across the
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