PERMFILE114378

• Permit No: C1994082
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Dodson & Associates Hydraulic Programs ‎(Trap, Pipe)‎
• Section_Exhibit Name: TAB 13 ATTACHMENT 13-1 ADDENDUM 2
• Media Type: D
• Archive: No

TRAPEZOIDAL AND CIRCULAR CHANNEL ANALYSIS HYDROCALC HYDRAULICS MANUAL. PAGE 12
The Trapezoidal Channel Analysis fI'RAP) program quickly computes the Normal Depth, Critical
Depth, Rating Curve. or Standard Step Water Surface Protlle for flow in a trapezoidal channel.
The Circular Channel Analysis (CIRC) program provides the same information for circular
channels.
Using the'IYapezoidal Channel Analysis program, you can qutckIy and easily analyze the hydraulic
chazacteristics of almost any trapezoidal channel, including those with a different side slope for
each bank. Triangular and rectangular channels can also be easily analyzed by the program,
because they aze both special kinds of trapezoidal channels. A trtangulaz channel is a trapezoidal
channel with a channel bottom width of zero. A rectangular channel is a trapezoidal channel with
side slopes of zero (vertical sides).
The Trapezoidal Channel Analysts and Circular Channel Analysis programs are appropriate for
open-channel flow only. Pressure flow in pipe and box culverts should be analyzed using the Pipe
Culvert Analysis and Box Culvert Analysts programs which are included in HYDROCALCm Hydtaulla.
2.1 NORMAL DEPTH FOR TRAPEZOIDAL OR CIRCULAR CHANNELS
Normal Depth is the depth at which uniform flow will occur in an open channel In other words,
if you had a uniform channel of infinite length, carrying a constant flow rate, then IIow in the
channel would be at a constant depth at all points along the channel, and this depth would be
the Normal Depth.
It is often useful to determine Norma] Depth, because it may represent a good apprvldmatlon of
the actual depth of flow within a channel segment. It 1s common practice to use Normal Depth
computations to prepare a preliminary design for channel improvements, and then to chec]c or
refine the design by computing the water surface profile !n the channel ustng the Standard Step
or DlreM Step Methods. The Standard Step procedure oftheTRAP and CDZC programs, for example,
can be used for further analysis of a preliminary channel design identified using the Normal Depth
procedure.
2.1.1 REAUIRED INPUT DATA FOR NORMAL DEPTH PROCEDURE
Instant help is avallable at all times during data entry, as described In Section 1.5 of this manual.
Pressing the er key on the upper left comer of your keyboazd will cause each of the HYDROCALC°
Hydraulics programs to display a box containing guidance on entering the required data.
2.1.1.1 Flow Rate
The user must supply the flow rate which the channel is to convey, m cubic feet per second Icfs).
Sometimes, the flow rate may vary through the length of a channel segment, because of local
inflow to the channel. In such cases, you must decide whether to base your analysis on the
mardmum flow rate or the average flow rate in the channel segment. Local drainage regulations
or practice may provide guidance in this regard. When In doubt, perform the analysis with each
IIow rate and compare the results.
2.1.1.2 Channel Bottom Slope
The channel bottom slope >s the average drop in elevation per foot of length along the channel.
For example, if the channel bottom drops 1 foot in a length of 1000 feet, then the channel bottom
slope >s 0.001 feet per foot. Channel bottom slopes are sometimes expressed in percent. A slope
of 0.001 feet per foot is the same as a 0.1% slope.
The slopes of the water surface and the energy grade line are assumed to be the same as the
channel bottom slope for normal flow conditions. Therefore, it is important to provide the best
possible estimate of the channel bottom slope.
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