Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The land adjacent to the creek in this reach is undeveloped at the present <br />time, but is projected to be developed with industriol and multiple-family housing <br />in the near future. <br /> <br />Examination of the post-flood channel profile provided by Adams County <br /> <br />indicates that two drop structures of 2-3 feet in height in combinotion with two <br /> <br />drop structures of 10-12 feet in height best fit the existing profile in this reach. <br /> <br />This results in channel slopes within the recommended range of .002 to .006 for <br /> <br />unlined channels. <br /> <br />A grass Ii ned channel was investigated and it was found that it would <br />encroach on the entire right-of-way thereby necessitating the purchase of addi- <br />tionalland if a green belt and service road are desired along the creek. Another <br />drawback to a grass lined channel is that velocities up to 7 fps would result dur- <br />ing a 10-year flood which is near the upper limit of allowable velocities for grass <br />lined channels. It was therefore decided to use side slopes on the order of 2 hori- <br />zontal to 1 vertical and protect against channel erosion by using rip rap channel <br />protecti on. <br /> <br />The existing channel depth in the reach is such that the lOO-year flood <br />can be occommodated within the channel with some widening of the existing natural <br />channel. Approximately 28 acres of land which is within the present 100-year flood <br />plain would become available for unrestricted development if the channel is de- <br />signed to accommodate the lOO-year flood flow. <br /> <br />On the basis of the above, it was concluded to design the chonne I to <br />accommodate the lOO-year flood flows utilizing two grouted riprap drop structures. <br />two concrete baffle drop structures and riprap channel protection between drop <br />structures. The reason for choosing grouted riprap over gab ions is the longer life <br />expectancy of grouted riprap. The only maintenance required with this design <br />will be cleaning debris which gets caught on the concrete drop structure baffle <br />blocks. This can be accomplished by hand labor utilizing summer student help. <br /> <br />111-3 <br />