FLOOD10334 ‎(2)‎

• Designation Number: 588
• County: Arapahoe
• County: Jefferson
• Community: Littleton
• Stream Name: Massey Draw and SJCD (South)
• Title: FHAD - Massey Draw and SJCD ‎(South)‎
• Date: 12/1/2005
• Prepared For: Urban Drainage and Flood Control District, Jefferson County, Littleton
• Prepared By: Olsson Associates
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Downstream of South Platte Canyon Road, the Centennial Water and Sanitation District has received
approval from the State Engineers Office for construction of the South Platte Reservoir. This project
includes a channel designed to convey the Probable Maximum Flood (PMF) from SJCD (South)
around the north side of the reservoir to the South Platte River. Construction of the PMF channel was
completed in 2005.

Photo 1 - Looking downstream of Carr
the August 1999 flash flood (UDFCD).

Photo 2 - East side of Carr Street, August 1999
(UDFCD).

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The SJCD (South) watershed is fully developed. except for some parcels between South Carr Street
and South Kipling Parkway.

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The North Tributary extends from its confluence with SJCD (South) downstream of South Platte
Canyon Road in a northwesterly direction to Pierce Court, The North Tributary has been improved
along its entire length, From Sheridan Court to West Ken Caryl Avenue a portion of the North
Tributary flows are conveyed in a 60-inch pipe.

Street after

Tributary No.1 extends from its confluence with SJCD (South) downstream of South Wadsworth
Boulevard west to Sangre de Cristo Road, The drainageway has been improved through Coronado
Park, between South Wadsworth Boulevard and South Carr Street. Tributary NO.2 extends from its
confluence with SJCD (South) upstream of Ken Caryl Avenue west to Continental Divide Road,

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SJCD (South) begins at South Platte Park and extends west to approximately South Simms Street.
has three tributaries and covers approximately 3.4 square miles

2.3

The County and UDFCD have constructed improvements on Massey Draw 'and the North Tributary
since the Original Plan was completed, Culvert improvements were constructed along South Kipling
Parkway in 1988. Culvert and downstream channel improvements were constructed at Carr Street in
1999. Channel stabilization improvements were constructed in 2002 on the North Tributary
downstream of Iris Street.

SJCD (South)

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Massey Draw begins at Chatfield Reservoir and extends west approximately three miles west of the
hogback and C-470, The North Tributary extends west from its confluence with Massey Draw east of
South Wadsworth Boulevard to Simms Street. The watershed covers approximately 9.0 square miles
The study limit is the hogback for Massey Draw and Continental Divide Road for the North Tributary.
The Massey Draw watershed is fully developed except for a parcel located southwest of South Carr
Street and West Chatfield Avenue and some in-fill parcels located throughout the watershed,

Flash flooding also occurred on Massey Draw on June 27, 2004. Rainfall was recorded as 2.96 inches
west of the hogback and 2,05 inches just northeast of Ken Caryl Avenue and C-470. An average
rainfall depth for the entire basin was not available, West Ken Caryl Avenue under C-470 was
reported to be flooded 2- to 3-feet deep. On the Deer Creek Golf Course, the flood flow split west of
the West Rockland Drive cul-de-sac bulb, with water flowing both north and south of West Rockland
Drive. It was estimated that approximately 75 percent of the water flowed north into the area between
West Coco Place and West Rockland Drive, The culverts under South Oak Street were overtopped
and the water flowed east into the detention pond (Pond #2), The detention pond did not have an
emergency overflow capable of handling the excessive flow from Massey Draw, Inadvertent detention
of stormwater was observed west of South Oak Street. Several homes along the north side of West
Rockland Drive were flooded to a depth of approximately three feet due to restricted culverts under
South Oak Street and West Rockland Drive (Photos 3 and 4). It is thought that a portion of the fences
along West Rockland Drive east of South Oak Street contributed to the structure flooding after
becoming plugged with debris, The Garrison Street culvert was severely eroded, and extensive
stream bank erosion occurred (Photos 5 through 8). By comparing the field evidence to the hydraulic
model results from this study, the flows were preliminarily estimated to approximate the 1 O-year storm
event. Massey Draw at the northwest end of the golf course was estimated to be flowing at
approximately 1000 cfs and the flow in the Meadow Ranch area was estimated to be in the range of
1200-1500 cfs. Information regarding other flood events in the study watershed is not available.

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The study area is located in southern Jefferson County, north of Colorado State Highway C-470 and
west of the South Platte River. The study area includes the Massey Draw and SJCD (South)
watersheds. The area east of South Platte Canyon Road is located in the City of Littleton. The
remainder of the study area is located in unincorporated Jefferson and Arapahoe Counties.

Massey Draw

On August 4, 1999 flash flooding occurred on Massey Draw (Photos 1 and 2) that resulted in stream
and localized urban flooding. The peak flow, at Carr Street was estimated to be 1100-1200 cfs by
taking cross sections and measuring high water marks, The flow was equated to approximately a 10-
year storm event based on the Original Plan, Flooding occurred in the area of the Deer Creek Golf
Course/Meadow Ranch development, which was under construction. Houses had not yet been
constructed at the time of the flash flooding

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Location

Flood History

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Watershed Description

City 0/' Littleton

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Flood Hazard Area Delineation
Massey Draw and SJCD (South)
December 2005