FLOOD00281

• County: Larimer
• Community: Greeley
• Title: Design Criteria and Construction Specifications volume 2 of 5 Storm Drainage Criteria
• Date: 10/1/1997
• Prepared For: Greeley
• Prepared By: Department of Public Works
• Floodplain - Doc Type: Educational/Technical/Reference Information

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11. Safety Requirements (Small Drainageway)

a.

A six-foot high vinyl coated chain Link or comparable
fence shall be installed to prevent access wherever the
100-year channel flow depths exceed three feet. Gates,
with top latch, shall be placed at 250-foot intervals and
staggered where fence is required on both sides of the
channel.

b.

Ladder-type steps shall be installed not more than 400
feet apart on alternating sides of the channel. Bottom
rung shall be placed approximately 12 inches vertically
above the channel invert.

5.5.4

Riprap Channel Lininas (Small DrainagewayI

The criteria for the design and construction of riprap channel
linings shall be in accordance with the USDCM, Volume 2, "Major
Drainage - Riprap." Riprap lined channel shall be designed for a
turbulence factor (Froude Number) less than 0.8 for the 100-year
flood peaks. The riprap shall be designed and constructed in
accordance with Section 10.2 of these criteria. Freeboard
requirements shall be in accordance with the standards for grass
lined channels (see Section 5.5.2).

5.5.5

other Lining TVDes (Small DrainagewayI

The criteria for the design of small drainageway channels with
linings other than grass, rock, or concrete will be dependent on
the manufacturer's recommendations for the specific product. The
applicant will be required to submit the technical data in support
of the proposed material. Additional information or calculations
may be requested by the City to verify assumptions or design
criteria. The following minimum criteria will also apply.

1. Flow Velocity (Small Drainageway)

The maximum normal depth velocity will be dependent on the
construction material used; however, the Froude Number shall
be less than 0.8.

2. Freeboard (Small Drainageway)

Same as for grass lined channels (see Section 5.5.2).

3. Curvature (Small Drainageway)

The center line curvature shall have a ml.nl.mum radius twice
the top width of the design flow but not less than 50 feet.
The minimum radius of curvature for channels with a loa-year
runoff of 20 cfs or less shall be 25 feet.

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