FLOOD03313

• County: Denver
• Basin: South Platte
• Title: Drop Structures in the Denver Metropolitan Area
• Date: 12/1/1986
• Prepared For: UDFDC
• Prepared By: McLaughlin Water Engineers, Ltd.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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that it was more economIcal to utIlIze multiple drops for grade control of a sand

bed stream (referred to as a sedIment transport channel) than to utilIze a continuous

liner. Further, It concluded that baffle apron drops were more economIcal (although

marginally so) than several other types of drops Including SOli Conservation Service

(SCS) vertical and Type C Basins, USBR Type IV, and TrapeZOIdal Grouted Riprap

uSing vertical drops. The design flow ranged from 1550 to 2010 cfs.

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The stream had previously degraded to the point of endangering adjacent properties.

Upon completion of the 3 phase construction project, the stream was stabilized. As

Illustrated In the photograph and confirmed by field Inspection, several drops need

further stabilizatIOn work along the banks, particularly below the drops. It IS also

interesting to note that the bottom row of baffles IS not level WIth the water

surface, indicating pOSSible seepage or settl1ng problems. Nevertheless, the structures

appear stable. Note that fenCing IS used for safety. The overall appearance IS

reasonable.

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Case 2 - NIver Creek at York

These drops were originally constructed In 1974 as part of a channel project that

Included a flprap channel l1ning. The deSIgn flow IS on the order of 2600 cfs. The

drops appear stable, but Illustrates the need for trickle channel provisions. The

originally constructed channel sectIon was a riprap trapezoidal section. Because

there is no trIckle channel through the crest, and also because the first row of

baffles Sit directly on the crest, aggradation occurs at most flows. (See Figure JI-2

and II-3). A naturally formed trickle channel exists in the aggraded material and IS of

a similar configuration to many others. The degree of aggradation would have

certainly been reduced by construction of a trickle channel through the crest. Also,

the photographs show very heavy, but also poorly graded rlprap in the banks above

the chute walls. Landscaping might have been more effective.

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Case 4 - East Harvard Gulch between Logan and DOWning
ThiS baffle chute, was deSigned to pass a 25-year discharge of 2000 cfs and also
to provide the hydraul1c control for a Side channel spillway whIch serves a flood
storage pond. Figures lI-4 and lI-S Illustrate aesthetic landscaping and architectural
treatments through the use of exposed aggregate finish and a decorative safety rail.

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II-3