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<br />areas are covered with tall grasses and weeds, along with light brush. <br />The Manning roughness coefficients for this reach are .040 for the main <br />channel and .045 for the overbank. <br />Several small streams and irrigation drainage ditches join Cedar <br />Creek in this reach near the county airpol't. Near station 20+00, Cedar <br />Creek is crossed by Highway 550 in a 144 inch diameter CSP. The Selig <br />Canal crOsses the stream in an overhead flume, and another roadway <br />crosses as a wooden bridge. The Denver and Rio Grande railroad crosses <br />at this point also on a wooden trestle. <br />As discussed above, along much of the Cedar Creek drainageway, <br />especially the upper reaches, the vegetative cover consists of heavy <br />growth (cedar, juniper, and sagebrush), with accompanying heavy ground <br />I itter. Significant quantities of this vegetation \li11 be carried by <br />the drainageway flows, particularly during the less frequent storms <br />when stream flows encroaching in the densely overgrown overbank areas <br />will pull additional vegetal matter into the waterway. This debris <br />will in turn snag on other vegetation and lodge against culvert entran- <br />ces, reducing the overall conveyance capabi'l ity of the stream. Because <br />of this blockage potential, the assigned roughness coefficients for all <br />streams are higher than otherwise," to bettel' reflect the continuous <br />nature of the debris blockage problem. Bridge and pipe ratings also <br />reflect the impact of the debris problem, as discussed in Section JJ,B <br />below. <br />Summary tables of roughess coefficients and bridge and culvert <br />data are included at the end of this repol't. <br />2. Montrose Arroyo <br />The upper st udy 1 i 111 it of Mont rose Arroyo is at the <br />confluence of several small tributaries which combine to form the main <br /> <br />7 <br />