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Last modified
11/23/2009 1:21:24 PM
Creation date
10/4/2006 9:31:47 PM
Metadata
Fields
Template:
Floodplain Documents
Designation Number
151
County
Elbert
Community
Elizabeth
Stream Name
Running Creek
Title
Floodplain Information Report - Running Creek and Drainage Study, Elizabeth, CO
Date
7/1/1979
Designation Date
1/1/1980
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />. <br />I <br />I <br />'. <br />I <br />I <br />I <br />I <br />. <br />I <br /> <br />in the middle and upper portions of the reach which are inundated <br />by the 100-year flood. These areas are undeveloped, and there <br />are no structures in the floodplain. The only major road crossings <br />in this reach are Kipling Street and 1-70. Kipling Street would <br />be inundated during a 100-year event, while the 1-70 bridge has <br />100-year capacity.- <br />The final reach in Jefferson County begins at 1-70 and contin- <br />ues upstream to the study limits for Clear Creek. For the most part, <br />the 100-year floodplain is confined in the banks of the channel with <br />average widths ranging from 150 feet to 250 feet. There is a large <br />ponding area just upstream from McIntyre Street. This ponding area <br />is due to backwater behind the McIntyre bridge with floodplain <br />widths extending to about 1,400 feet. However, there are no build- <br />ings in the floodplain in this area. At the Coors complex in Golden, <br />flows exceed channel capacity and would inundate several buildings. <br />Upstream from the Coors complex, the 100-year floodplain is mostly <br />confined on the south bank with the exception of one area at Ford <br />Street. The north bank does not confine the flows, and the flood- <br />plain reaches widths of approximately 600 to 700 feet. The very <br />upper portion of the reach to the limit of the study is again <br />basically confined with floodplain widths of about 200 to 300 feet <br />There are a couple of houses that would be affected by the 100-year <br />event. Major road crossings in this reach include McIntyre Street, <br />West 32nd Avenue, Ford Street, Washington Street and U.s. Highway 6. <br />Ford Street and Washington Street are the only crossings in this <br />reach with less than 100-year capacity. <br />The limits of laO-year flooding for Clear Creek are graphically <br />outlined on the Flood Hazard Area Delineation maps and tabulated <br />in Table I, Floodplain and Floodway Reference Data. The table <br />lists the potential flood elevations, floodplain and floodway <br />widths, floodway location, floodway surcharge elevation and thalweg <br />elevation at each cross section studied. <br />A floodway represents a part of the floodplain which is re- <br />quired to pass a laO-year flood event without raising the flood <br />profiles more than an acceptable amount and also represents the <br />part of the floodplain most hazardous to personal safety and welfare. <br /> <br />Throughout this study, in Adams County, Jefferson County, Arvada, <br />Wheat Ridge, Golden and Denver, the floodway was defined as the <br />limit of encroachment into the floodplain which raises the exist- <br />ing water surface elevations by no more than one-half foot. Fur- <br />ther restrictions in Adams County include in the floodway areas <br />with velocities exceeding 3 feet per second, or depths in excess <br />of 18 inches. In the unincorporated areas of Jefferson County, <br />the floodway also includes the floodplain with velocities exceed- <br />ing 3 feet per second, and depths exceeding one foot. For the <br />short reach in the City and County of Denver, additional floodway <br />restrictions include areas exceeding 18 inches of depth. Flood- <br />way widths, which represent the maximum allowable limits of en- <br />croachment into the floodplain, are tabulated in Table I. <br /> <br />Flood Velocities <br /> <br />Average flow velocities characteristic of a 100-year flood <br />event for Clear Creek are shown on the profile sheets included <br />with the Flood Hazard Area Delineation drawings. The flow velo- <br />city in the channel ranges generally between 3 and 15 feet per <br />second for a lOa-year flood event in the study area. Overbank <br />velocities range from 2 to 5 feet per second. <br />Water flowing at a rate greater than 6 to 8 feet per second <br />will cause severe erosion of stream banks and is capable of trans- <br />porting large rocks. Velocities in the range of 6 to 8 feet per <br />second could erode fill around bridge abutments. Water flowing <br />at about 2 feet per second or less will deposit debris and silt. <br /> <br />- SUMMARY - <br /> <br />This report has identified the probable flooding limits of <br />a potential 100-year flood event in the Clear Creek drainage basin. <br />The floodplain limits are based on (1) planned, future develop- <br />ment in the basin; (2) existing and mapped floodplain conditions; <br />and, (3) no blockage at the existing culvert and bridge structure. <br />Even with these assumptions, floods of greater magnitude can and <br />will occur in which the limits of flooding would exceed those <br />shown in the report. <br /> <br />-7- <br />
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