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<br />Therefor: <br /> <br />V2 <br /> <br />Y2 <br /> <br />J' <br />2 <br />120 Dso '3 <br /> <br />or <br /> <br />Y2 = <br /> <br />Qi <br /> <br />J <br />"7 <br /> <br />(2a) <br /> <br />2 <br />,. , <br />120 Dso - 1\-2 <br /> <br />A dimensionless form of equation 2 can be written if flow <br />continuity can be assumed for the approach and contracted <br />segments of the flood plain being analyzed, That is: <br /> <br />Q2 = C:. = Tf1 Jv:.. j:. <br /> <br />then <br /> <br />Y2 W 2. V2 <br /> (_-") 7 [ 1 , (2b) <br />= <br />Y1 W 1 2 <br /> 2 ,. Ds1 <br /> 120 Y: - <br /> <br />The above contraction scour equations were developed for <br />hand computations: and are based on rather limiting <br />assumptions. For example they are based on homogeneous bed <br />materials and would not apply for stratified layers of <br />different bed mat:erials. However, with clear-water scour <br />in stratified materials using the finest DSD would give the <br />worst case scour depths, Also, the equations could, in the <br />clear water case, be used sequentially for stratified bed <br />materials. TheSE! equations are the best that are available <br />and should be reqarded as a first level of analysis. If a <br /> <br />14 <br />