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SECTION 1 - STREAM CORRIDORS <br />Keeping the Balance <br />In any given reach, a stream constantly adjusts itself. It is balancing the <br />amount of water, the gradient of the channel, and the amount and size of the <br />sediment. The size of the channel is determined by the stream's energy, slope, <br />and flow of water in balance with the size and quantity of the sediment <br />particles the stream moves. <br />A major disturbance or many small disturbances, either natural or human- <br />caused, can alter this balance. Human activities - such as diverting or adding <br />water, building in floodplains, or removing vegetation - can limit a stream's <br />ability to maintain a balance. An unbalanced stream is an unhealthy stream. <br />Erosion Isn't Always Bad <br />We often think of erosion as the culprit that degrades streams, but erosion is a <br />natural process. A healthy stream bank may erode a small amount each year. <br />Erosion becomes destructive to streams when it increases above the normal <br />rate. Then it takes land away from wildlife and agriculture, and reduces the <br />quality of water that fish and other aquatic life need. Soil or sediment eroded <br />upstream is deposited somewhere downstream and builds a stream bank <br />(process of aggradation). <br />15 <br />prom Kosgen (1996), from Lane, Proceedings, 1995. In: Stream Corridor Restoration: Principles, Processes, and <br />Practices. By the Federal Interagency Stream Restoration Working Group (FISRWG). Reproduced with the per- <br />mission of American Society of Civil Engineers.