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A FEW COMMENTS ABOUT STREAMS
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HOW STEAMS "BEHAVE"
(Stream Dynamics)

River, stream, creek, brook, tributary, or branch ¾ these words all mean different things to different people.  Throughout this publication, the word "stream" means any continuous or intermittent flowing water ¾ regardless of the channel size.

It is the nature of a stream to change its course, constantly shift, and meander.  Erosion of streambanks is a natural part of this process by which the steam adjusts to changing conditions within the channel and its watershed.  If you try to interfere with this process, you will be in a long-term battle against the natural tendency of the stream to move and change.  However, because of man's development, especially in urban areas, this process may be accelerated.

The shape of the stream channel is a result of the flow of the water, the sediment carried, and the composition of the streambed and streambank materials.

A stream channel must simultaneously accommodate the flow and carry its sediment load within the streambanks.  The stream forms a continuous system of pools, riffles, bars, and curves to absorb the energy of the flow.  See Figure 1.  The adjustments a stream makes create a balance between the amount of water flowing in the channel, the amount of sediment it is transporting through the channel, and the changing slope and size of the channel.  The erosion of channel bends along outside banks is usually offset by deposition along inside banks.

Streams are rarely perfectly straight.  What appears to be a "straight" stream is in reality made up of small curves not easily recognized.  Flowing water has a natural tendency to meander from one side to of a channel to the other, and soil, sand, and gravel are washed away from the areas where the current is fastest and deposited where the water moves more slowly.