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<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 />Flood Hazard <br />Page seven <br /> <br />Siltation <br /> <br />Constriction of culverts and ditches through siltation <br />reduces or eliminates their flow capacity. and deposition in <br />detention ponds reduces or eliminates their storage capacity. <br />The low point in the detention pond was shown as 8370.5 on the <br />May 1979 topographic map and as 8370.6 on the January 1986 <br />topographic map. Mr. Kirvelevicius experienced the deposition <br />of silt on his lawn and his driveway from the June 4, 1986 <br />flood. Photos he provided showed various culverts partly or <br />completely blocked by silt. Silt was deposited in the <br />detention pond upstream of Kelley Road. Other photos <br />documented erosion on roads. roadside ditches and some of the <br />"natural" channels. <br /> <br />It is reasonable to expect, based on the photographs <br />described above. that the "theoretical" culvert capacities and <br />detention capacities could be reduced during a significant <br />"actual" flood. If that were the case, a 5-year flood could <br />overtop Kelley Road. <br /> <br />Historic SUbdivision Practices <br /> <br />Not unlike other communities in Colorado, the subdivision <br />of land in the Woodland Park area has not historically included <br />much consideration of natural drainageways, as shown in Figure <br />4. a portion of the town's property map. Some lots have <br />encroached into or crossed natural drainages. In many of the <br />subdivisions no improvements to natural swales or channels were <br />required, and there are apparently no requirements for dealing <br />with potential siltation. <br />