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The river slope was determined via a measurement of its elevation change over a 100 foot <br />distance centered at the dike repair. The Manning's numbers selected for each subsection were <br />selected from Design Hydrology and Sedimentology of Small Catchments. Table 4 shows what <br />material conditions each Manning's n corresponds to. <br />Table 4 - Manning's Number <br />Surface Conditions Mannin 's n <br />Shales and hardpans 0.025 <br />Graded silts to cobbles when collodial 0.03 <br />Sluggish river reaches, rather weedy <br />or with very deep pools <br />0.06 <br />3. Conclusions <br />The determined velocity along the dike slope, according to Manning's equation, is 3.34 fps. This <br />is less than either the velocity limit in erosive (5 fps) or in non-erosive (7 fps) soil. In addition to <br />vegetation along the slope, the presence of large size boulders at the slope base and J-hooks <br />upstream will protect the slope from erosion even during a 100 year event. <br />Tri County Dike Slope Stability Jan 08 12