Laserfiche WebLink
<br />B. Peak Flows at Design Points <br />The discharges resulting from analysis of the basin tributary to <br />the ephemeral drainageway seems to confirm observations by the county <br />road maintenance personnel. <br />With the design storm located to produce the most severe flooding <br />where the ephemeral drainageway flows north to the railroad embankment <br />(~ mile east of the intersection of Colorado State Highway 34 and the <br />Burlington Northern Railroad tracks), the 100 year recurrence interval <br />discharge is 390 cubic feet per second (cfs). The storm water will <br />back up behind the embankment approximately 5 feet deep with a resulting <br />storage of 40 acre-feet. The peak discharge through the culverts in <br />the embankment will be 70 cfs and flow will be sustained above 40 cfs <br />for 16 hours. With the storm centered over the basin downstream of the <br />railroad embankments, the 100 year discharge resulting at the ephemeral <br />drainageway crossing of Detroit Street (Colorado Highway 59) will be <br />490 cfs, much of which is produced by the urbanized portion of the basin. <br />The use of flood detention in these urbanized areas would limit discharges <br />in this swale to approximately 320 cfs. Figures 12 and 13 show appropriate <br />channel configurations to carry the 320 cfs and 490 cfs discharges. <br />The channel should be seeded with natural grasses which will limit <br />extensive erosion until the velocity exceeds 3\ feet per second. <br />Flood discharges in the currently urbanized basins are generally <br />conveyed in several streets as opposed to concentrating in a well-defined <br />swale. Discharges have been shown on Figures 4 through 7 at major design <br /> <br />-14- <br />