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10000 .10
n IS ROUGHNESS COEFFICIENT IN MANNING
9000
FORMULA APPROPRIATE TO MATERIAL IN
BOTTOM OF CHANNEL
8000
1.0
Z IS RECIPROCAL OF CROSS SECTION
.08
7000
.07
6000
REFERENCE: H.R.B. PROCEEDINGS 1946,
PAGE 150, EQUATION (14)
.8
5000
.06
.7
4000
.05
100
.6
EXAMPLE: (SEE DASHED LINES) 70
3000
50
GIVEN : S = 0.03
.04
.5
Z = 24 30
Z/n = 1200
n = .02
20
2000
y = 0.22
.4
FIND : Q = 2.0 CFS .03
10
7
5
3
.3
1000
2
900 .02
800
1
700
.7
600
.5 .2
500 .3
.2
400
.1
.01
300 .07
.05
.008
.03
INSTRUCTIONS
200 .02
.007
1. CONNECT Z/n RATIO WITH SLOPE (S) .1
AND CONNECT DISCHARGE (Q) WITH
DEPTH (y). THESE TWO LINES MUST
.01
.006
INTERSECT AT TURNING LINE FOR
COMPLETE SOLUTION.
.08
.005
.07
100
T
90
2. FOR SHALLOW
.004
.06
80
V-SHAPED CHANNEL
y
AS SHOWN USE NOMOGRAPH
70
WITH Z = T
y
60
.05
.003
50
y'
a
.04
40
b
y
3. TO DETERMINE ( X )
DISCHARGE Q IN Z
x
30
PORTION OF CHANNEL X
.002
HAVING WIDTH X:
.03
DETERMINE DEPTH y FOR TOTAL DISCHARGE IN
ENTIRE SECTION a. THEN USE NOMOGRAPH TO
DETERMINE Q IN SECTION b FOR DEPTH
b
20
y' = y - ( X )
Z
y'
b .02
a
4. TO DETERMINE DISCHARGE y
( X )
IN COMPOSITE SECTION: -
Za
FOLLOW INSTRUCTION 3.
Z b y' .001
10 TO OBTAIN DISCHARGE IN X
SECTION a AT ASSUMED
= Z (y - y')
DEPTH y : OBTAIN Q FORb a
SLOPE RATIO Z AND DEPTH y' THEN Q T= Q + Q
b a b
.01
7-42 DESIGN AND CONSTRUCTION STANDARDS Effective: November 16, 2000
RATIO Z/n
DISCHARGE (Q) IN CFS
TURNING LINE
SLOPE OF CHANNEL (S) IN FT/FT
DEPTH AT CURB OR DEEPEST POINT (y) IN FT
FIGURE 7-11
GUTTER CAPACITY REDUCTION CURVES
1.0 1.0
.9 .9
s=0.6% s=0.6%
F=0.8 F=0.8
.8 .8
MINOR STORM MINOR STORM
.7 .7
MAJOR STORM MAJOR STORM
.6 .6
s=0.4% s=0.4%
F=0.5 F=0.5
.5 .5
.4 .4
.3 .3
BELOW MINIMUM BELOW MINIMUM
ALLOWABLE ALLOWABLE
STREET GRADE STREET GRADE
.2 .2
.1 .1
.0 .0
0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14
SLOPE OF GUTTER (%) SLOPE OF GUTTER (%)
REDUCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY REDUCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY
WHEN APPROACHING AN ARTERIAL STREET LOCAL AND COLLECTOR STREETS
APPLY REDUCTION FACTOR FOR APPLICABLE SLOPE TO THE THEORETICAL GUTTER APPLY REDUCTION FACTOR FOR APPLICABLE SLOPE TO THE THEORETICAL GUTTER
CAPACITY TO OBTAIN ALLOWABLE GUTTER CAPACITY APPROACHING ARTERIAL STREET CAPACITY TO OBTAIN ALLOWABLE GUTTER CAPACITY APPROACHING ARTERIAL STREET
Effective: November 16, 2000
DESIGN AND CONSTRUCTION STANDARDS
7-43
REDUCTION FACTOR, F
REDUCTION FACTOR, F
Table 7-7: Allowable Cross Street Flow
Street Classification Minor Storm Runoff Major Storm Runoff
Residential and Local Street Maximum Depth of 6 Inches in Maximum Depth of 18 Inches Above
Cross Pan Flowline
Collector Street Where Allowed, Maximum Depth Maximum Depth of 18 Inches Above
of 6 Inches in Cross Pan Flowline
Arterial Not Allowed Maximum Depth of 6 Inches Over
Street Crown
7.11 Culverts
(A) System Design
(1) Required: Culverts shall be provided for the conveyance of storm water runoff under a
roadway, railroad, driveway, or other crossings of an open drainage system (such as a
drainageway or roadside swale). The size, shape, and type of culvert crossings shall be
based on the projected runoff volumes, as well as existing topographic conditions. All
culvert designs are subject to approval by the Director.
(2) Culvert Types: Typical culvert types include circular, elliptical, or arch pipe sections,
and reinforced concrete box culverts.
(B) Hydraulic Design
All culverts shall be designed using the form presented in Figure 7-12,  Design Computation Form for
Culverts, of these Standards. The procedures and basic design methods to be applied are in accordance
with the UDFCD Drainage Criteria Manual. All culvert designs are to include an analysis to determine
whether inlet or outlet control conditions govern for both major and minor storm runoff conditions. The
following procedure is to be applied:
(1) Compile design data, including design discharge, allowable headwater, and proposed
culvert cross section (to determine slope, length, flowline and velocity).
(2) Design culvert assuming inlet control, using trial culvert type and size. Apply the proper
design nomographs and repeat until the allowable headwater condition is achieved.
(3) Design culvert assuming outlet control, beginning with the adequate culvert design for
inlet control. Compute H (Head) from the proper design nomograph and TW (Tail
Water) from open channel hydraulics to determine HW (Headwater). The HW must
satisfy the allowable headwater conditions.
(4) Design appropriate outlet protection based on outlet velocity and tail water depth.
7-44 DESIGN AND CONSTRUCTION STANDARDS Effective: November 16, 2000
Effective: November 16, 2000 DESIGN AND CONSTRUCTION STANDARDS 7-45
(C) Structural Design
The structural design of culverts shall conform to accepted structural engineering practices, the Colorado
Department of Transportation design standards and standard specifications, any methods and criteria
recommended by the manufacturer for a specific culvert type, and for conditions found at the construction
site. As a minimum, all culverts shall be designed to withstand an AASHTO HS-20 traffic loading.
(D) Specifications
(1) Size
(a) Culvert design size shall be based upon the following:
(i) Runoff volumes for the appropriate design storm.
(ii) Required capacity based on roadway classification and allowable street
overtopping, as prescribed in Section 7.10,  Street Drainage, of these
Standards
(b) Culverts shall be at least 18 inches in diameter or height, with the exception of
driveway culverts along roads with roadside drainage swales, which shall be at
least 12 inches in diameter or height.
(2) Inlet and Outlet Sections
(a) All culverts shall be designed with headwalls and wingwalls, or flared end
sections at the inlet and outlet. Flared end sections are allowed only on pipe
culverts with diameters of 42 inches (or equivalent) or less.
(b) Erosion protection, such as rip-rap, boulder energy dissipators, or adequate
vegetation, shall be provided at the inlet or outlet where required to mitigate
potential scouring or erosive flow conditions. The Engineer shall propose the
erosion protection to be used, subject to approval by the Director.
(3) Slope and Velocity [ Pobierz całość w formacie PDF ]

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