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5 6 I I I I I I I I I I I I I I I I I I I II. DESCR!PTION OF THE RIVER exists. The high bank has old cottonwoods with a ground cover of grass. The new deposits of sediment ere colonized with willows and some cottonwood seedlings. 7. Therefsevidenceofbe<lverandmuskrats. Geeseandducksllse the river for water and a safe resting place. General The plan and profile of the South Platte River from Chatfield Dam to Brighton ;s shown 1n Appendix t. The reach of river drops approximately 430 feet 1n 41.2 miles. In the downstream direction the river passes through or adjacent to Jefferson County, Douglas County, Arapahoe County Columbine Valley, littleton, Englewood, Sheridan, City of Denver, Commer~e City, Thornton, Adams County, and Brighton. The reach is in the juris. diction of the Urban Drainage and Flood Control District. The major tributaries in the study reach are Bear Cnee~, Cherry Cnek, Sand Creek and Clear Creek. The left bank tributaries, Bear Creek and Clear Cree~, supply more streamflow than the right bank tributaries, Cherry Cree~ and Sand Creek. Bear Creek and Cherry Creek are dammed for urban flood control. The Chatfield Dam on the main stem is also a flood control structure. 8. 9. There is relatively little trash. Works of men are few, Bridges, diversion weirs and houses are far apart. There fs little or no ban~ protection. The floodplain is used mainly for agriculture or the mining of gravel. Suburban River. The suburban river differs from the rural river in aspects: these The study reach of the South Platte River is composed of three dist~nct types of rivers, herein calle~ Rural, Suburban, and Urban. Any vestlge of the pristine South Platte Rlver has been lost for some time. The natural streamflow regime has been changed by the upstream flood and water supply reservoirs, by direct diversions from the river and its tributaries and I:>y the importation of water from the Colorado River Basin known as the Western Slope. Inaddition,thesupplyofsedimenttothe river has been arrested by the dams and by bank control works through the middle portions of the study reach which prevent the river from moving laterally in its valley. Rural River. Inthestudyreach,theSouthPlatteRiverpasses through some areas which are essentially rural. The characteristics of the river here are as follows: 1. The river meanders through its flOOdplain in a sinuous manner. 2. The river is free to move laterally by eroding one bank and building the other, There 1s little or no bank protection. 3. As a result of lateral movement, the river has one high bank and onl:'lowbank. 1. Some meander loops have been cut off, decreasing the sinuosity of the river. 2. Some eroding banks have been stabilhedwith rubble--a mixture of broken concrete, asphalt, and bricks along with other excavated materials. 3. There are more bridges, weirs, intakes and sewer outfalls. 4. There are many more houses aM other buildings on the floodpla1n. 5. There is much more trash in and along the river: car bodies, old furniture and appliances, such as stoves and refrigerators, garbage in sacks, and piles of rubble. 6.Insomelocations,thefloodplainonthelowbankhasbeenfi1led with excavated materials. 7. There are less gravel and sand bars and less native vegetation. Tn some places, rock outcrops on the river bed. The suburban river is sti1l wide and shallow in some places and there is evidence of wildlife. 4. The river is wide and shallow. The low-flow channel has gravel and sand bars on thl:' inside of the bends and in the middle or sides of the channel at other locations. The riverbed is sand or gravel. 5. Some bars are vegetated with willows whiCh are the pioneer vegetation. Urban River. The urban river takes on more characteristics of a man-made ditch. Itreta1nsfewcharacteristicsoftheruralriver. The features of the urban river are as follows: 6. On the river banks, the natural succession of vegetation st1l1 1. Tnechannelhasbeenstraightenedandrealignedtosuitthe desires of people. There is very little sinuosity left. 2. The river is narrow and relatively deep compared to the rural rlver. The narrowing has been accomplished by raising the low bank and extending it out into the former riverbed. Both banks are much higher than in the rural areas.