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<br />I <br />II <br />II <br />I <br />I <br />I <br />I <br />'I <br />I <br />I <br />I <br />II <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />STREAM TYPES <br /> <br />The stream types shown in Figure 1 constitute the five base classifications (referred to by the <br />notation ST-l to ST.5). The classification relates the fundamental variables of alluvial channel <br />dynamics: water discharge, sediment transpon, bed-material size, and stream grade to relative <br />channel stability. The following are brief descriptions of each stream type. <br /> <br />Stream Type ST-l <br /> <br />General Description: Straight channel pattern with mostly suspended bed-material sediment <br />transport. The stream bed profile has rime-pool sequences. These are low-power streams that <br />are easily diverted from a straight alignment by topographic constraints. <br /> <br />Comment: In natural channels, a straight channel pattern indicates a stream with a meander <br />wavelength much larger than the normal 10 to 14 times stream width (see EQ.4, Stream Channel <br />Geometry). Straight streams show distinct oscillation in the channel bed in the form of rime- <br />pool sequences. A straight channel will contain a succession of riffles and pools (at about 5 to 7 <br />time the channel width) around each bend. Bends occur because the stream is confined between <br />valley bluffs which divert the stream back and forth across the valley floor. In this case, the <br />sinuosity of the stream should be estimated as the sum of riffle to rime distances. <br /> <br />Relative Stability: Stable <br />Uncenainty: Slight, shifting of riffle-pools within channel <br />Sinuosity, P: 1.0 - 1.05 <br />Stream Type ST-2 <br /> <br />General Description: Straight channel pattern with a mixed sediment transpon mode <br />(contact and suspended bed-material sediment transport). This stream type is slightly more <br />powerful compared to ST-l and possesses pre-meandering ~atures such as longitudinal and <br />medial bars. These streams ~ are easily diverted from a straight alignment by topographic <br />constraints. <br /> <br />Comment: Straight channels with a mixed sediment transport show some lateral as well as <br />vertical oscillation in the channel bed. Lateral features are in the form of alternate bars or <br />dissected riffles indicating an increase in the organization and power of secondary currents. <br />However, these channels are still too low-powered to produce a lateral oscillation in the stream <br />bank. <br /> <br />Relative Stability: Stable <br />Uncenainty: Slight, shifting of alternate bars within channel <br />Sinuosity, P: 1.0 - 1.05 <br /> <br />5 <br />