| Stream Gradient |
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Information AboutStream Gradient |
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A stream that flows upon a uniformly Erodable substrate will tend to have a steep gradient near its source, and a low gradient nearing zero as it reaches its Base Level . Of course a uniform substrate would be rare in nature; hard layers of Rock along the way may establish a temporary base level, followed by a high gradient, or even a Waterfall , as softer materials are encountered below the hard layer. Human Dam s, Glaciation , changes in Sea Level and many other factors can also change the "normal" gradient pattern. On Topographic Map s, stream gradient can be easily approximated if the scale of the map and the contour intervals are known. Contour lines form a V-shape on the map, pointed upstream. By counting the number of lines that cross a stream bed within a measured distance, and converting this to the actual measurements of the land surface, will determine the actual gradient. For example, if one measures a scale mile along the stream length, and counts 3 contour lines crossed on a map with ten-foot contours, the gradient is approximately 30 feet per mile, a fairly steep gradient. |