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<br />H. Step 5. Incipient me,tion analysis. <br /> <br />1, Bed material is fine to medium sand. <br /> <br />2. Not a factor for Los Gatos Crleek analysis. <br /> <br />3. An incipient motion analysis will be illustrated In the Lesson 6 <br />workshop. <br /> <br />I. Step 6. Evaluate arrnoring potentii311. <br /> <br />1. Armoring occurs when the bed becomes coated with a layer of <br />coarse material, due to selective tl'ansport of the finer bed material <br />by the flow, <br /> <br />2. For Los Gatos Creek there was no armorin9 potentiall because <br />bed material is sand. <br /> <br />3. An armoring potential analysis. will be illustrated In the Lesson 6 <br />workshop. <br /> <br />J. Step 7. Evaluation of rating curve shifts, <br /> <br />1. When stream gage data are available. analysis of the <br />stage-discharge rating curve over time can provide insight on stream <br />stability. <br /> <br />2. The most common cause of rating curve shifts in natur'al channel <br />control sections is generally scour and fill. Therefore, a rating curve <br />that was stable but suddenly shifts may be indicative of a change in <br />the watershed causing increased channel erosion or sedimentation, <br /> <br />3. The rating cunle for Los Gatos Greek walS too indeterminate to <br />analyze. <br /> <br />K. Step 8. Evaluate SCI:>ur conditions, <br /> <br />1. Evaluation of scour conditions using the methods presented in <br />HEC-18 is the final step in a Level 2 analysis of stream stability at <br />bridge crossings, <br /> <br />2, The three components of scour at bridge crossings are local scour, <br />contraction scour and aggradation/degradation, <br /> <br />5,9 <br />