Laserfiche WebLink
<br />should extend up the side slopes a distance of Yn + l' as projected from <br />the downstream channel or the critical depth plus one foot whichever is <br />greater. The side slopes for the chute and downstream apron should be <br />the same as the crest wall and upstream channel with the exception that <br />a riprap slope as steep as 2:1 can be used starting above the riprap <br />lining height required above. The thickness of the riprap immediately <br />downstream of the crest wall should be increased to DRW as shown in <br />Table 1. This overthickening is necessary to protect the most critical <br />area of the structure. The voids in the apron can be filled during <br />construction to reduce ponding of low flows in the apron area. <br />6. The downstream channel should be the same as the upstream <br />channel, including a trickle channel. The trickle channel invert must <br />be below the top of the adjacent riprap section to insure that trickle <br />flows will drain into the trickle channel. For concrete trickle <br />channels a foundation wall similar to the one used for the upstream <br />trickle channel should be use. In some instances the wall may also be <br />used to control seepage and piping. <br /> <br />EXAMPLE PROBLEM <br /> <br />~~ <br /> <br />GIVEN: <br /> <br />Q = 1600 cfs <br />Upstream and downstream channel dimensions <br /> <br />bottom width = 50 ft. <br />side slopes = 4:1 <br />Yn = 4.0 ft. <br /> <br />s = .0043 ft./ft. <br />Yc = 2.9 ft. <br />Yn = 6.0 fps <br /> <br />Erosion resistant soils <br /> <br />7 <br />