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<br />,.~OOJ7 <br /> <br />Stream Physics and Channel Materials <br /> <br />Reduced habitat complexity and the loss of pool depth tends to truncate the <br />diversity of resident species and associated age classes. This often leads to <br />stream systems with fewer species, limited age classes, and reduced long-term <br />productivity. Changes in habitat are typically the .result of changes in land <br />use conditions and road systems, changes in watershed response and peak flows, <br />changes in bank stability, changes in sediment and water supply, changes in <br />the availability of large woody debris, or changes in the temperature regimes <br />such as higher summer or lower winter pool temperatures. <br /> <br />Stream physics and channel materials are therefore key to understanding Stream <br />Health. Because biological interactions are so complex, the direct measure of <br />biological integrity, if not impossible, is at least very expensive. As an <br />alternative, integrity is inferred from habitat conditions and environmental <br />effects based on predicted changes in stream physics and channel materials. <br />The intent of the Photo Section is to help visually define some of the <br />elements used to assess Stream Health. <br /> <br />The photos compare some physical conditions that support Stream Health and <br />some that do not. Referring to the list from the law (Page 2), the photos <br />illustrate several water quality related effects or conditions: <br />Natural temperature and flow patterns. <br /> <br />Concentration/dispersal of pollutants. <br /> <br />Sediment accumulation. <br /> <br />, <br /> <br />Road construction, use, and maintenance impacts. <br /> <br />- Changes in the hydrologic cycle (natural flow levels or peaks). <br /> <br />Accelerated storm runoff effects on erosion and sedimentation. <br /> <br />Roads are of particular concern because they create permanent changes and <br />trigger many of the effects listed above. So much damage is generated by <br />roads that special attention is needed if Robust Stream Health is to be <br />achieved. In spite of both legal requirements and technical guidance to the <br />contrary, streams are frequently treated as gutters and not as an integral <br />piece of the landscape. Culverts, for example, may unintentionally destroy <br />the ability of fish to migrate. The photos show some of these conditions. <br />The end result is a continuing major loss of Stream Health along many streams. <br /> <br />When runoff is allowed to concentrate, the erosive power and transport power <br />increase exponentially. If the increase is great enough, the channel widens <br />with accelerated erosion of beds and banks. As natural drainage patterns are <br />modified, storm flow patterns respond with accelerated stream sedimentation. <br /> <br />Text Page 5 <br /> <br /> <br />. ' <br />