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<br />1.1 THE STREAM AND ITS VALLEY
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<br />Cherry Creek is a right-bank plain tributary of the South Platte River, entering the river in a highly
<br />developed business and industrial area of Denver. The Cherry Creek watershed is about 54 miles
<br />long and averages 10 miles wide. The creek flows north-northwest from the upper end of the
<br />watershed located about 10 miles northeast of Colorado Springs, to its confluence with the South
<br />Platte River.
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<br />The Cherry Creek watershed upstream from Franktown has steeply to moderately rolling topography
<br />with ponderosa pine growing on the higher ridges. The Cherry Creek valley is, in general, "v"-
<br />shaped. In the reach from near Franlctown to near Parker, Cherry Creek courses through a broader
<br />valley bordered by steep to rolling ridges and hills. Downstream from Parker, the uplands become
<br />less rough and the watershed lies in a rolling plain area The watershed slopes northward from
<br />elevations of about 7,700 feet m.s.L at the source of Cherry Creek to about 5,600 feet m.s.L at the
<br />upstream end of Cherry Creek Park to about 5,170 feet m.s.L at the confluence with the South Platte
<br />River. Vegetation is mostly pasture grass and agricultural crops with some forested areas in the
<br />foothills portion of the watershed.
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<br />The Cherry Creek watershed is semiarid. Warm summers and mild to cold winters occur. Intense
<br />thunderstorm rainfalls, sometimes of cloudburst intensity, occur during the summer months. The
<br />following table gives climatological data in the vicinity of the Cherry Creek watershed.
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<br />Table 1
<br />Cherry Creek Watershed Vicinity Climatological Data *
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<br />Parker6E,TownofParker 1948-1997 14.1 70.7 28..9
<br />Cherry Creek Dam 1951-2001 17.0 72.1 30.3
<br />Castle Rock 1948 - 2001 16.9 69.3 29.0
<br />· This data was obtained from the High Plains Regional Climate Center Website online@hoccsun.unLedu
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<br />Cherry Creek is formed by the confluence of East Cherry Creek and West Cherry Creek about 8
<br />miles upstream from Franktown. From the confluence of East Cherry and West Cherry Creeks to
<br />Lake Gulch, Cherry Creek has an average stream gradient of approximately 100 feet per mile. From
<br />Lake Gulch to a point about 2 miles south of Franktown, Cherry Creek passes through a narrow,
<br />steep-walled canyon (Castlewood Canyon), dropping 400 feet in about 5 miles. In the vicinity of
<br />Franktown, Cherry Creek enters a broad, ''v''-shaped valley about three-fourths of a mile wide.
<br />From Franktown to the Cherry Creek Reservoir, the stream channel averages 200 feet wide and
<br />ranges from 2 to 10 feet deep. The bed has an average slope of 25 feet per mile. The channel is
<br />alluvial, flat bottomed, and follows a meandering course.
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<br />The reach of Cherry Creek studied in this report begins at Scott Road, approximately 7 miles
<br />upstream from the Parker town limit or about 7.5 miles downstream from the U.s. Geological
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<br />Survey stream gauging station located in central Section 15, T.8S, R. 66W at Castlewood Canyon. The study reach
<br />ends about 1 mile downstream from Colorado State Highway 88 (Arapahoe Road). Figures 1 through 17 show
<br />existing conditions along the study reach, upstream to downstream respectively.
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<br />1.2 CHERRY CREEK CORRIDOR
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<br />The Cherry Creek Corridor Study area is located in portions of Townships 5S, 6S, 7S and 8S, Range 67W and 66W
<br />and 65W, and includes portions of Arapahoe and Douglas Counties, the Town of Parker and City of Aurora
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<br />The Cherry Creek Corridor watershed area above the reservoir is approximately 386 square miles and includes
<br />portions of Arapahoe, Douglas and El Paso counties. '
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<br />The main developed areas along the reach of Cherry Creek studied in this report are Parker and Aurora Parker,
<br />which is located in the southeast comer of the Denver metropolitan area, was established in 1864 at the location of
<br />Twenty-Mile House, a hotel at the junction of Cherry Creek Road and the Smokey Hill Stage Line. Agriculture is
<br />the primary economic activity in the upstream end of the reach studied in this report. However, downstream of
<br />Stroh Road, the area has been developed into a booming residential and commercial center with a 2002 population
<br />of32,000.
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<br />The study corridor consists of approximately 16.5 miles of channel and floodplain which drops from an elevation of
<br />5,955 feet at Scott Road to 5,606 feet at the upstream end of the reservoir (349 feet of elevation change). The
<br />average bed slope within the corridor is approximately 0.004 feet/feet. Physiography of the watershed is quite
<br />variable - consisting of pinyon pine covered hillsides, short grass prairie, and canyons.
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<br />The major stream in the study area is the main stem of Cherry Creek. Ephemeral streams tributary to Cherry Creek
<br />within the study reach include Piney Creek, Happy Canyon Creek, Newlin Gulch, Scott Gulch, Tallinan Gulch, Oak
<br />Gulch, Baldwin Gulch and Lemon Gulch. The main stem of Cherry Creek is a perennial waterbody that has a wide,
<br />shallow, well-defined channel that meanders through the majority of its length, with Cherry Creek Reservoir
<br />located at the study reach terminus.
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<br />1.2.1 Stream Characteristics
<br />Cherry Creek is the major surface water stream within the watershed, supporting its own alluvial aquifer. Cherry
<br />Creek and the aquifer are hydraulically connected; therefore, changes in water table elevations affect conditions in
<br />the creek and many segments of the creek go dry as a result of well pumping in the Cherry Creek alluvium. Flow in
<br />Cherry Creek results from precipitation, alluvial groundwater discharge, stormwater nmoff, and return flow
<br />discharges from advanced wastewater treatment plants. Temporal variations in flow are due to snowmelt runoff
<br />and summertime storm events. Snowmelt runoff is observed early, typically starting in March, and continuing
<br />through May. (Cherry Creek Basin Water Quality Authority (CCBWQA, 2000).
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<br />1.2.2 Reservoirs
<br />There are no major flood control reservoirs within the study reach. In the 1 960s, the Natural Resource
<br />Conservation Service (NRCS) constructed 32 minor flood-control structures in the Cherry Creek upper watershed
<br />as part of the "Franktown-Parker Tributaries of Cherry Creek Watershed" and the "West Cherry Creek Watershed"
<br />projects. The structures were constructed for design floods having an approximately 25-year recurrence interval
<br />and generally affect only normal flows an small storm events in the upper watershed on Cherry Creek and offer
<br />limited flood protection downstream of the dams (CCBWQA, 2000). In 1933, the Castlewood Canyon Dam,
<br />located upstream ofFranktown breached during a major storm event that resulted in significant damages and loss of
<br />life.
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