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I I I I I I I I I I I I I I I I I I I flowing full will intercept some of the runoff and convey it to where it is not wanted. There also is a history of the canal becoming clogged with silt and debris, necessitating periodic cleaning to make the canal operative. The Middle branch tributary of 0054-1 drains a small drainage basin immediately east of the main stem of Direct Flow Area 0054-1. The channel remains in a natural state with the exception of 112th Avenue, a small retention pond, and the Colorado Agricultural Canal, all of which cross the channel. The floodplain is narrow due to the surrounding topography and the small amount of area contributing to drainage, Sheet 11. There is no base or trickle flow except for possibly during irrigation season. However, once the upper part of the basin reaches a fully developed condition, a constant trickle flow may develop. With the possible exception of periodic silting of and interception of flow by the canal, potential flood hazards remain small. The Northern branch of 0054-1 drains the area that lies parallel to the basin which drains the Middle branch of 0054-1. This channel also remains in a predominently natural state, and the floodplain remains narrow as it travels a steep course, Sheet 12. The Colo- rado Agricultural Canal appears to be the only place where silting and interception of storm rUDoff constitute any real flood hazards. As flow overtops Riverdale Road, downstream land area is SUbjected to some shallow, but limited flooding. Direct Flow Area - 0054-2 The upstream region of the cllannel of Direct Flow Area 0054-2, in Adams County, has a very narrow floodplain because the topography is dominated by the surrounding hills and ridges. The channel remains predominantly in a natural state except for a small pond and tlle Colorado Agricultural Canal, both of which have been constructed across it, Sheet 13. Beneath Riverdale Road exists a 12 inch CMP which is capable of only conveying low flows. Below Riverdale, the Lower Clear Creek Canal crosses the floodplain. Both the Lower Clear Creek and Colorado Agricultural Canals could potentially become plugged with silt and debris transported by storm runoff and require periOdic cleaning. Also, unwanted storm waters could enter these canals, creating inconveniences elsewhere along the canal. Because of the absence of a well-defined channel below Riverdale, flow widens out abruptly, often making impoSSible to discern exact floodplain limits. With the exception of a single farmhouse exposed to shallow flooding, the flood damage potential remains small. -28- Direct Flow Area - 0054-3 The Southern Branch of Direct Flow Area 0054-3 also remains essentially in a natural state except for a few small ponds, road crossings, and canals which have been constructed across it. Above Riverdale Road, the channel remains fairly uniform in width, widening out only at an occasional pond and at Riverdale, Sheet 16. Below Riverdale Road, the channel becomes less well defined, and the 100-Year floodplain widens con- siderably, Sheet 17. As the channel crosses the Colorado Agricultural and Lower Clear Creek Canals, both unwanted flows entering the canal and silt deposition represent nuisances and potential flood hazards which exist due to the lack of a formal wasteway. The Northern and Southern Branches combine below Riverdale, and the floodplain remains wide as flow continues for approximately 650 feet where it encounters a private road, Sheet 18. As runoff ponds behind the road, flow is distributed over the road as it travels northeast to a low spot in the road where it crosses. From here, the drainage swales become wide and shallow, making the 100-Year floodplain limits difficult to discern as flow frequently exceeds the limits of the sWale, Sheet 19. From the Upstream Study Limits to where the northern branch intersects with Quebec Street, the 100-Year floodplain remains confined to the channel banks and no significant flood hazard exists, Sheet 20. Where the channel crosses the Colorado Ag- ricultural Canal, both unwanted runoff entering the canal and silt deposition pose potential problems. Quebec Street and Riverdale Road are overtopped as the 18 and 15 inch CMP's placed beneath them, respectively, are only suitable for low flows, Sheet 21. As flow continues, it intersects the lower Clear Creek Canal, where problems as previously described for the Colorado AgriCultural Canal exist as well.