FLOOD03016

• County: El Paso
• Community: Colorado Springs
• Stream Name: Arkansas River and Tributaries
• Basin: Arkansas
• Title: Areawide Urban Runoff Control Manual
• Date: 9/28/1979
• Prepared For: Pikes Peak Area Council of Governments
• Prepared By: Gilbert Meyer & Sams
• Floodplain - Doc Type: Miscellaneous

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Izzard, for computation of flows in street sections is:

Q = 0.56 Z d8/3 Sl/2
n

where:

Q-=-capaci!y in triangular (half street) section, cfs

Z = reciprocal of cross slope, feet per foot

n = Manning's roughness coefficient

d = depth of flow at face of curb, feet

S = street grade, feet per foot

Figure IV-2 is a nomograph for the solution of this equation.
A direct solution for a composite section may be obtained by
substituting Z3 into the previous equation. Z3 is defined as:

Z3

= Zl [ 1

+ (Z2/Z1-1)

( T W ) 8/3]
T+W(Z2/Z1-1)

wher.e:

Z3 = reciprocal of cross slope of equivalent section,
feet per foot
Zl = reciprocal of cross slope of gutter, feet per foot
Z2 = reciprocal of cross slope of pavement, feet per foot

T = top width of water surface, feet
_W_- =-Width of gutter, feet

Because of debris, velocity limitations, and the probability
of parked vehicles, the theoretical capacities calculated by the
above methods must be adjusted to obtain allowable design values.
The ratio of allowable to theoretical capacity is given in
Figure IV-3. For arterial streets the flow shall be limited
to provide one unobstructed traffic lane in each direction or
the value from Figure IV-3, whichever is less.

C. Culverts

Culverts shall be designed according to procedures outlined
in Hydraulic Charts for the Selection of Highway Culverts,
Hydraulic Engineering Circular No.5, Dec. 1965, and Capacity
Charts for the Hydraulic Design of Highway Culverts, Hydraulic
Engineering Circular No. 10, March 1965, both publications of
the U.S. Department of Commerce, Bureau of Public Roads.

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