Q U I C K  2
Computer Program
COMPUTATION OF WATER SURFACE
ELEVATIONS IN OPEN
CHANNELS
VERSION 1.0
JANUARY 1995
QUICK2
Computation of Water Surface Elevations in Open Channels
User's Guide
Federal Emergency Management Agency
1995
TABLE OF CONTENTS
Page
Chapter 1: INTRODUCTION
1 1
Chapter 2: OVERVIEW . . .
2 1
Chapter 3: GETTING STARTED
3 1
Chapter 4: TUTORIALS
. .4 1
N
. . . . . 4 2
Changing Variables
. . . 4 6
Ste
. . . . . .. . . 4 9
Running HEC2 with QUICK2 Files . . .. . 418
Rerunning Using Saved CrossSection Files 419
Chann
421
R
422
423
Profile Plot
423
CrossSection Plot
424
Chapter 5: FORMULAS
5 1
Cri
. . . . . 5 2
Chann
. . . . . 5 4
Normal Depth . . . . . . . . . . . . . . . . . 5 5
StepBackwater
5 6
Appendix 1: DEFINITION OF VARIABLES
A 1
QUICK2 User's Guide
Introduction
Chapter 1: Introduction
QUICK2 is a user friendly program that assists in the computation of flood
Water Surface Elevations (WSEs) in open channels of all types. It is much
easier to use than the United States Army Corps of Engineers (USACE) HEC2
program. However, a QUICK2 stepbackwater file can also be used, as is,
with the HEC2 program, which is also included in the QUICK2 package of
programs. Therefore a HEC2 output file can be generated with a QUICK2 input
data file, without ever leaving the QUICK2 environment; and, without having
to know how to setup and run the HEC2 program. This version of QUICK2
(Version 1.0) however, does not perform hydraulic calculations through
bridges or culverts.
QUICK2 was primarily developed to accompany the FEMA technical guidance
manual titled, "MANAGING FLOODPLAIN DEVELOPMENT IN ZONE A AREAS  A GUIDE FOR
OBTAINING AND DEVELOPING BASE FLOOD ELEVATIONS." That manual is intended to
assist local community officials who are responsible for administering and
enforcing the floodplain management requirements of the National Flood
Insurance Program (NFIP). The purpose of that manual is to provide guidance
for obtaining and developing base flood (100year) elevations (BFEs) where
Special Flood Hazard Areas (SFHAs) on a community's Flood Hazard Boundary Map
(FHBM) or Flood Insurance Rate Map (FIRM) have been identified and designated
as Zone A.
QUICK2 will also be useful to community engineers, architect/engineer firms,
developers, builders and others at the local level who may be required to
develop BFEs for use in Special Flood Hazard Areas.
This manual includes four other chapters: Overview, Getting Started,
Tutorials and Formulas. The Formulas section describes the "complex"
equations and methodologies used in the development of the program. An
Appendix is also included that contains a list of Definitions of the
variables shown on the screen and on the printouts.
To get started as quickly as possible in using QUICK2 we
recommend that the user read the Overview and Getting
Started chapters; and then work through the Tutorials.
MINIMUM SYSTEM REQUIREMENTS
Random Access Memory (RAM) 512K
Hard disk storage 800K
Monitor Color or Monotone
Printer (prints to LPT1) Dotmatrix to LaserJet
Disk Operating System (DOS) Version 3.0 or higher
11
QUICK2 User's Guide
Overview
Chapter 2: Overview
. FOUR OPTIONS
This user friendly program computes:
• Critical Depth,
• Cross Section Capacity (Rating Curves),
• Normal Depth, and
• StepBackwater Analysis (similar to the USACE HEC2 program)
CRITICAL DEPTH: This option should be used to determine a Base Flood
Elevation (BFE) if a previous calculation using the Normal Depth option
computed a depth that was determined to be SUPERCRITICAL. Super Critical
depths are generally not accepted for use as BFEs.
CHANNEL CAPACITY: This option is used to determine a rating curve for a cross
section. The program computes a discharge based on the entered depth.
Repeating with other depths produces a rating curve. A BFE may be determined
by interpolation with the correct discharge.
NORMAL DEPTH: This is the usual option to use in determining BFEs. The user
should watch the "Flow Type" message to make sure that the calculation is
CRITICAL or SUBCRITICAL. Use Option 1 if SUPERCRITICAL.
STEPBACKWATER: This option should be used to calculate BFEs if more than one
crosssection is warranted to cover the extent of the property. Generally if
the property parallels more than 500 feet of a flooding source this option
should be used.
. HANDLES "REGULAR" AND "IRREGULAR" SHAPED CROSS SECTIONS
The REGULAR shape crosssections include:
• Vshape,
• Trapezoidal,
• Rectangular, and
• Circular
21
QUICK2 User's Guide
Overview
For IRREGULAR crosssections:
 up to 40 points can be input to describe the ground points
 Ground points are easily modified using the Insert or Delete Keys
 Encroachments or other changes in the floodplain are easily modeled
 An unlimited number of cross sections may be modeled
In addition, ground points and other input variables for the irregular shape
crosssections can be saved to a file, for later use.
. SINGLE SCREEN DATA INPUT, COMPUTATION AND OUTPUT
One of the most userfriendly aspects of this program that sets it apart from
many other computational programs is that all of the data input, the
computation, and the printing or plotting, is performed from the same screen.
You will not get lost in a maze of menus.
. GRAPHICS
• CrossSection Plots,
• Water Surface Elevation Profiles, and
• Rating Curve Plots
Cross section plots and water surface elevation profiles from QUICK2's step
backwater analysis can be viewed on the screen using the USACE PLOT2 program
that comes with the QUICK2 package of programs. The channel capacity option
of QUICK2 can be used to generate rating curve plots of individual cross
sections that can be viewed on screen and printed.
. AUTOMATIC ERROR CHECKING
This software is designed to virtually eliminate the need for user's manuals.
The program incorporates errorchecking routines and warning messages to
alert the user to incorrect input data or potentially incorrect output data.
The program prompts the user for the required input data so that there is no
need to worry about which columns to put data in; whether or not it needs to
be leftjustified, or right justified, etc.
22
QUICK2 User's Guide
Overview
SPECIAL FEATURES OF QUICK2
»» Critical Depth, Channel Capacity, and Normal Depth Options ««
EASY VIEW: All of the input data is viewed on the same screen (and changes
can be made) before starting the computations
EASY CHANGE: After an initial calculation, the following parameters can be
changed, and the above options can be recalculated in seconds:
Discharge Channel Slope Manning's N
Base width or Diameter Channel Side Slope Ground Points
Channel Stations
AUTOSAVE: For irregular channels the program automatically stores all the
input variables to a file designated as "TEMP.XSC", which is stored in the
C:\QUICK2\DATA Directory.
RATING CURVES: A special feature of the Channel Capacity Option for irregular
channels is the Rating Curve Print Option. A rating curve plot can be
automatically generated with 20 computations of water surface elevation
versus discharge. The maximum elevation of the rating curve will be just
lower than the channel depth specified by the user. The rating curve can be
viewed on the screen and/or printed.
»» StepBackwater Option ««
EASY VIEW: All of the input data is viewed on the same screen (and changes
can be made) before starting the computations
PRECISE: Balances the energy equation to within .01 foot.
COMPUTES CRITICAL DEPTH AUTOMATICALLY: After up to 40 energy balance trials
(without a balance) the program automatically computes critical depth.
OUTPUT OPTIONS: Detailed and Summary printouts are available
AUTOSAVE: The program automatically saves the first crosssection into a
file designated as T0.XSC, and subsequent crosssections are saved adding the
Channel distance (XLCH) to the previous crosssection's file name.
Therefore, if we run 3 crosssections that are 200 feet apart their
filenames will be: T0.XSC, T200.XSC, and T400.XSC. These files are
automatically stored in a directory named C:\QUICK2\DATA.
HEC2 RUNS WITH QUICK2 FILES: The backwater option also automatically saves
all of the crosssections into a HEC2 compatible file called HEC2.DAT, which
is stored in the C:\QUICK2 Directory. The QUICK2 program is linked with the
USACE HEC2 program such that any backwater computation that is run using
QUICK2 can also be run using the HEC2 program within the QUICK2
environment. The user does not need to have any previous experience in
running the HEC2 model.
23
QUICK2 User's Guide
Overview
AUTOMATIC ERROR CHECKS AND WARNING MESSAGES
ERROR CHECKS
Error checks prevent the user from continuing by reprompting the user for
correct input data. The following are error checks performed automatically by
the program:
 Ground Point (GR) stations should be increasing
 Stations of the left and right bank should match a GR point
WARNING MESSAGES
Warning messages instruct the user that the program has had to modify the
input data in order to complete a calculation, or that the completed
calculation may not be valid. The following are warning messages performed by
the program:
Extended Cross Section
The computed water surface elevation is higher than one or both ends of the
crosssection, and the program automatically extended the end(s) of the
crosssection vertically to complete the computation.
Divided Flow
There is a ground point(s) within the crosssection which is higher than the
computed water surface elevation which is dividing the flow within the cross
section.
No Energy Balance ... Computing Critical Depth
The program attempted up to 40 trial computations and could not arrive at an
energy balance; and therefore, critical depth is assumed to occur at this
crosssection.
Computing Critical Depth ... Critical Depth Assumed
Either the initial Starting Water Surface Elevation or an energy balance
between two cross sections occurred at an elevation for which the froude
number or the index froude number was equal to or greater than 1. Thus, the
computed water surface elevation is suspected of being below the critical
depth. Therefore the critical depth is computed and compared to the previous
calculated water surface elevation. In this case the critical depth elevation
was higher, and thus Critical Depth is Assumed.
Computing Critical Depth ... Critical Depth Not Assumed
Same as above except, the critical depth is computed and compared to the
previous calculated water surface elevation; and, in this case the critical
depth elevation was lower, and thus Critical Depth is Not Assumed.
24
QUICK2 User's Guide
Getting Started
Chapter 3: Getting Started
This section provides you with
convenient installation and run
procedures that will enable you
to run the program from the hard
disk drive or the floppy disk drive.
Computer icon
HARD DISK INSTALLATION AND RUN PROCEDURE
To install and run QUICK2 simply place the floppy disk in either your "A"
disk drive or your "B" disk drive.
For "A" Drive users: Type A:\AQ2 and Press
For "B" Drive users: Type B:\BQ2 and Press
Follow the screen message to start the program. That's it!
The program resides in a C:\QUICK2 directory. To run the program in the
future, just change to that directory and type Q2 and press .
FLOPPY DISK INSTALLATION AND RUN PROCEDURE
To install and run QUICK2 from the floppy disk drive simply place the floppy
disk in either your "A" disk drive or your "B" disk drive.
For "A" Drive users: Type A:\FAQ2 and Press
For "B" Drive users: Type B:\FBQ2 and Press
Follow the screen message to start the program. That's it!
To run the program in the future, just place the disk in your floppy drive,
change to that directory and type Q2 and press . Although the
program will run from the floppy disk drive it will run much faster if
installed and run on the hard disk drive.
REMINDER:
Entering and editing data, as well as moving around within the input screens
is performed using the Function keys, the Backspace Key and the Enter Key. DO
NOT USE THE CURSOR CONTROL KEYS (ARROW KEYS) FOR ENTERING, DELETING, OR
EDITING DATA.
31
Chapter 4: TUTORIALS
Normal Depth
StepBackwater
Channel Capacity
PLOT  2
Chapter 4  Intro Image
{TIME REQUIRED TO COMPLETE ALL THE TUTORIALS IS ABOUT ONE HOUR}
41
Quick2 User's Guide page 42
QUICK2 User's Guide
NORMAL DEPTH {Tutorial Time: 5 to 10 minutes}
After pressing Q2 and to start the program you will come to
Main Menu screen of QUICK2 as shown below.
QUICK  2
MAIN
Press

Critical Depth
Channel Capacity
Normal Depth
StepBackwater
QUIT
 Help
1. Press 3 and then press to start the Normal Depth Option.
Next you will see the Shape of Cross Section screen:
SHAPE OF CROSS SECTION
Press
V  Ditch
Rectangular Channel
Trapezoidal Channel
Circular
Irregular
 Main Menu
Let's try the Trapezoidal Channel option.
2. Press T and then press to perform a Normal Depth calculation
for a trapezoidal channel.
42
Normal Depth Tutorial
the
MENU
1
2
3
4
V
R
T
C Channel
I Channel
Quick2 User's Guide page 43
QUICK2 User's Guide
The next screen you will see is the Input / Output screen:
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V)
Bottom Width (ft)
Discharge (cfs)
Slope (ft/ft)
OUTPUT VARIABLES
Area (sq ft)
Velocity (ft/s)
Top Width (ft)
Flow Type
Enter Left Side Slope
< Back Tab
The program is currently prompting you to enter the Left Side Slope (in
terms of the Number of Horizontal feet (H) to every 1 foot Vertical (H :
1). Let's say our left side slope is 3 to 1 (3:1).
3. Enter 3 and then Press .
The next screen you will see is the Input / Output screen with a new
prompt:
NORMAL Notice that the
TRAPEZOIDAL CHANNEL 3 has been entered
to the right of
INPUT VARIABLES "L Side Slope (H:V)"
L Side Slope (H:V) 3.0:1
Bottom Width (ft)
Discharge (cfs)
Slope (ft/ft)
Normal Depth Tutorial
DEPTH
:1 R Side Slope (H:V) :1
Manning's n
Depth (ft)
Wet Perimeter (ft)
Hyd Radius
Froude #
:1 and Press
Main Menu
DEPTH
:1 R Side Slope (H:V)
Manning's n
Depth (ft)
OUTPUT VARIABLES
Area (sq ft) Wet Perimeter (ft)
Velocity (ft/s) Hyd Radius
Top Width (ft) Froude #
Flow Type
line
Quick2 User's Guide page 43 bottom part
Enter Right Side Slope
< Back Tab
The program is currently prompting you to enter the Right Side Slope (in
terms of the Number of Horizontal feet (H) to every 1 foot Vertical (H :
1). Let's say our right side slope is 2 to 1 (2:1).
4. Enter 2 and then Press .
43
:1 and Press
Main Menu
Quick2 User's Guide page 44 top part
QUICK2 User's Guide
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft)
Discharge (cfs)
Slope (ft/ft)
OUTPUT VARIABLES
Area (sq ft)
Velocity (ft/s)
Top Width (ft)
Flow Type
Enter ".............."
< Back Tab
The program will continue to prompt you for input data.
Let's say our channel is 10 feet wide, with a Manning's n value of 0.035,
the discharge is 300 cfs, and the channel slope is .005 ft/ft.
SCREEN PROMPT  "Enter Bottom Width
5. Enter 10 and then Press .
SCREEN PROMPT  "Enter Manning's n
6. Enter .035 and then Press .
SCREEN PROMPT  "Enter Discharge
Normal Depth Tutorial
DEPTH
R Side Slope (H:V)
Manning's n
Depth (ft)
Wet Perimeter (ft)
Hyd Radius
Froude #
and Press
Main Menu
" and Press
" and Press
" and Press
Quick2 User's Guide page 44 bottom part
7. Enter 300 and then Press .
SCREEN PROMPT  "Enter Slope
8. Enter .005 and then Press .
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft) 10.0 Manning's n 0.0350
Discharge (cfs) 300 Depth (ft) 0.00
Slope (ft/ft) 0.0050
OUTPUT VARIABLES
Area (sq ft)
Velocity (ft/s)
Top Width (ft)
Flow Type
Begin Calculations
< Back Tab
and Press
DEPTH
R Side Slope (H:V)
Wet Perimeter (ft)
Hyd Radius
Froude #
Main Menu
"
After all the data
is input your screen
should look like this
44
Quick2 User's Guide page 45
QUICK2 User's Guide
To begin the calculation simply ...
9. Press .
After a split second the screen should look like this:
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft) 10.0 Manning's n 0.0350
Discharge (cfs) 300 Depth (ft) 3.27
Slope (ft/ft) 0.0050
OUTPUT VARIABLES
Area (sq ft) 59.6 Wet Perimeter (ft) 27.7
Velocity (ft/s) 5.0 Hyd Radius 2.2
Top Width (ft) 26.4 Froude # 0.6
Flow Type SUBCRITICAL
Begin Calculations
Print
< Back Tab
Notice that the Depth is no longer 0.00, but equals 3.27 feet, which is the
Normal Depth for this particular Trapezoidal crosssection. If 300 cfs
represents the 100year discharge, then the 100year flood depth would
equal 3.27 feet. All of the output variables have also been computed and
listed.
10. To print the output simply Press the Function key.
The printed output is shown below.
QUICK 
NORMAL DEPTH
Trapezoidal Channel
INPUT
___
^

Depth

_v_
Base Width =
Slope
45
Normal Depth Tutorial
DEPTH
R Side Slope (H:V)
Main Menu
2
OUTPUT VARIABLES VARIABLES
3.27 Depth (ft) / \
300.0 Discharge (cfs) 1 / n = 0.035 \ 1
5.04 Velocity (ft/s) / ____ ____ \
26.4 Top Width (ft) 2.0 / \ 3.0
0.59 Froude No. \____________/
SUBCRITICAL Flow Type: 10.0
= 0.0050
Quick2 User's Guide page 46
QUICK2 User's Guide
CHANGING THE VARIABLES
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft) 10.0 Manning's n 0.0350
Discharge (cfs) 300 Depth (ft) 3.27
Slope (ft/ft) 0.0050
OUTPUT VARIABLES
Normal Depth Tutorial
DEPTH
R Side Slope (H:V)
Area (sq ft)
Velocity (ft/s)
Top Width (ft)
59.6 Wet Perimeter (ft) 27.7
5.0 Hyd Radius 2.2
26.4 Froude # 0.6
Flow Type SUBCRITICAL
line
Quick2 User's Guide page 46 bottom section
Begin Calculations
Print
< Back Tab
Let's say we want to run this calculation again but with a discharge of 500
cfs instead of 300 cfs.
1. Press the Function Key
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft) 10.0 Manning's n 0.0350
Discharge (cfs) 300 Depth (ft) 3.27
Slope (ft/ft) 0.0050
OUTPUT VARIABLES
Area (sq ft) 59.6 Wet Perimeter (ft) 27.7
Velocity (ft/s) 5.0 Hyd Radius 2.2
Top Width (ft) 26.4 Froude # 0.6
Flow Type SUBCRITICAL
Enter Slope
< Back Tab
The above screen is what you should be looking at. The key will move
the prompt backwards through all the variables. Note that since we want to
change the Discharge (from 300 to 500), we will need to Press again to
come to the Enter Discharge prompt. Follow the steps as shown on the
following page to rerun this calculation with a new discharge.
46
Main Menu
DEPTH
R Side Slope (H:V)
and Press
Main Menu
Quick2 User's Guide page 47
QUICK2 User's Guide
SCREEN PROMPT  "Enter Slope
2. Press .
SCREEN PROMPT  "Enter Discharge
3. Enter 500 and then Press .
SCREEN PROMPT  "Enter Slope
4. Press .
After all of the data is input your screen should look like this:
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft) 10.0 Manning's n 0.0350
Discharge (cfs) 500 Depth (ft) 3.27
Slope (ft/ft) 0.0050
OUTPUT VARIABLES
Area (sq ft) 59.6 Wet Perimeter (ft) 27.7
Velocity (ft/s) 5.0 Hyd Radius 2.2
Top Width (ft) 26.4 Froude # 0.6
Flow Type SUBCRITICAL
Begin Calculations
< Back Tab
Normal Depth Tutorial
" and Press
" and Press
" and Press
DEPTH
R Side Slope (H:V)
Main Menu
47
Quick2 User's Guide page 48
QUICK2 User's Guide
5. Press to begin the calculation.
After a split second the screen should look like this:
NORMAL
TRAPEZOIDAL CHANNEL
INPUT VARIABLES
L Side Slope (H:V) 3.0:1 2.0:1
Bottom Width (ft) 10.0 Manning's n 0.0350
Discharge (cfs) 500 Depth (ft) 4.22
Slope (ft/ft) 0.0050
OUTPUT VARIABLES
Normal Depth Tutorial
DEPTH
R Side Slope (H:V)
Area (sq ft)
Velocity (ft/s)
Top Width (ft)
Quick2 User's Guide page 48 a
Quick2 User's Guide page 48 b
Quick2 User's Guide page 48 c
86.7 Wet Perimeter (ft) 32.8
5.8 Hyd Radius 2.6
31.1 Froude # 0.6
Flow Type SUBCRITICAL
line
Quick2 User's Guide page 48 middle section
Begin Calculations
Print
< Back Tab
Let's return to the Main Menu... Just Press the Function Key
QUICK 2
MAIN
Press

Critical Depth
Channel Capacity
Normal Depth
StepBackwater 4
QUIT
Main Menu
MENU
1
2
3
 Help
Quick2 User's Guide page 48 bottom section
If you want to continue and to perform the StepBackwater
Tutorial, then turn to the next page.
If you want to exit out of the program for now, Press .
48
Quick2 User's Guide page 49
QUICK2 User's Guide
STEPBACKWATER {Tutorial Time: 20 to 25 minutes}
Let's say that we have a piece of property located in an unnumbered Zone A,
and we need to determine if our property is really in or out of the
floodplain. We will be referring to Figure 1 on the next page which
represents a plan view of our proposed floodplain study (stepbackwater
analysis). We have field surveyed 3 crosssections to use in the step
backwater analysis. The next page lists all of the data from the field
surveyed crosssections.
If you have continued from the previous Normal Depth Tutorial you should
see the screen below. If you are just starting the program, you will see
the screen below after pressing Q2 and .
QUICK  2
MAIN
Press

Critical Depth
Channel Capacity
Normal Depth
StepBackwater
QUIT
 Help
1. Press 4 and then press to start the StepBackwater Option.
Next you will see the Starting Water Surface Elevation Method screen:
Starting Water Surface Elevation Method
Input
NORMAL DEPTH (SlopeArea)
Enter the Slope in Ft/Ft
OR
KNOWN WATER SURFACE ELEVATION
Enter the known WS Elevation
Enter a Slope or an Elevation:
Let's say that we do not have any previous information about flood
elevations for our sample stream. Thus we need to start the stepbackwater
analysis assuming that the flow in our first crosssection is at Normal
Depth. (This assumes that the channel slope downstream of our first cross
section will approximate the slope of the energy grade at the first cross
section of our study.) Let's assume that our calculated downstream channel
slope is .0029 ft/ft.
2. Type .0029 and then press .
49
StepBackwater Tutorial
MENU
1
2
3
4
.0025) (for ex.
656.78) (for ex.
QUICK2 User's Guide
StepBackwater Tutorial
CROSS SECTION INFORMATION
CrossSection 1
GROUND POINTS
Station Elevation
362 505.0
425 499.1
509 498.0
512 496.9
602 496.9
605 498.2
732 500.1
1020 504.7
CHANNEL BANK STATIONS
Left 509 Right 605
MANNING'S N VALUES
Left .065
Channel .040
Right .060
CHANNEL REACH LENGTHS
Left 
Channel 
Right 
LOSS COEFFICIENTS
Cont Expan 
100YEAR DISCHARGE
3000
Quick2 User's Guide page 410 a
CrossSection 2
Station Elevation
0 510.0
150 504.8
233 502.2
236 500.9
331 500.9
334 501.8
402 505.5
591 510.1
Left 233 Right 334
Left .055
Channel .040
Right .060
Left 450
Channel 450
Right 450
Cont 0.1 Expan 0.3
3000
Quick2 User's Guide page 410 b
CrossSection 3
Station Elevation
0 515.0
433 510.1
600 506.3
614 504.9
701 504.8
725 506.5
866 511.1
1240 514.6
Left 600 Right 725
Left .065
Channel .040
Right .060
Left 490
Channel 490
Right 490
Cont 0.1 Expan 0.3
3000
FIGURE 1
Quick2 User's Guide page 410 Figure 1
410
Quick2 User's Guide page 411
QUICK2 User's Guide
The next screen you will see is the Input / Output screen as shown:
XSEC ID:  BACKWATER <<
STAT
CHANNEL BANK STATIONS:
MANNING'S
CHANNEL REACH LENGTHS:
LOSS
WS ELEV
EG ELEV
F2}<Back Tab F5}List Files F6}Retrieve File F7}Main Menu F10}Ed/Ex GrPt
F3}Insert GrPt F4}Delete GrPt F1 }HELP
Before we go on let's read about how data is to be input for this screen.
3. Press to access the Help screen.
4. When you are finished reading the Help screen just Press .
If you refer to the previous page, you will see a tabulation of the Ground
Points for the first field surveyed crosssection listed by Station and
Elevation. You will also see the Channel Bank Stations, Manning's N values,
and Discharge.
5. Following the method explained in the Help Screen, enter the Ground
Points one at a time, by their respective Station and Elevation. Be sure to
Press after you have typed in each correct number.
Once you have entered all of the Ground Points correctly ...
6. Press to Exit from entering Ground Point data
NOTE: The Key will EXIT you from the top of the screen, or it will
RETURN you to the top of the screen if you need to go back to EDIT the
Ground Points.
StepBackwater Tutorial
>> STEP 0 POINTS GROUND
ELEV STAT ELEV STAT ELEV STAT ELEV
Right Left
Right Channel Left VALUES: N
Right Channel Left
:Dschrg Expansn COEFFICIENTS: Contractn
Kratio Top Wid Depth
Froud# ChanVel Flow Regime
411
Quick2 User's Guide page 412
QUICK2 User's Guide
Your screen should now look like this:
XSEC ID:  BACKWATER <<
STAT
362
602
CHANNEL BANK STATIONS:
MANNING'S
CHANNEL REACH LENGTHS:
LOSS
WS ELEV
EG ELEV
F2}< Back Tab F5}PRINT F6}SAVE F7}Main Menu F8}New XSEC F10}Ed/Ex GrPt
Enter
The program is currently prompting you to enter the Left Channel Bank
Station. Using the information contained on the previous page, we know that
our Left Channel Bank Station is 509. Therefore ...
7. Enter 509 and then Press . (Notice that the 509 has been
entered to the right of "CHANNEL BANK STATIONS:
Next you will see the Input / Output screen with a new prompt:
SCREEN PROMPT  "Enter RIGHT Channel Bank Station and Press "
Using the information for Crosssection 1, simply follow the screen prompts
to input the required data, as follows:
SCREEN PROMPT  "Enter RIGHT Channel Bank Station and Press "
8. Type 605 and then Press .
SCREEN PROMPT  "Enter
9. Type .065 and then Press .
SCREEN PROMPT  "Enter CHANNEL Manning's n Value and Press "
10. Type .040 and then Press .
SCREEN PROMPT  "Enter
11. Type .060 and then Press .
SCREEN PROMPT  "Enter Discharge
12. Type 3000 and then Press .
412
StepBackwater Tutorial
>> STEP 0 POINTS GROUND
ELEV STAT ELEV STAT ELEV STAT ELEV
496.9 512 498.0 509 499.1 425 505.0
504.7 1020 500.1 732 498.2 605 496.9
Right Left
Right Channel Left VALUES: N
Right Channel Left
:Dschrg Expansn COEFFICIENTS: Contractn
Kratio Top Wid Depth
Froud# ChanVel Flow Regime
and Press Channel Bank Station LEFT
Left".)
" and Press LEFT Manning's n Value
" and Press RIGHT Manning's n Value
" and Press
Quick2 User's Guide page 413
QUICK2 User's Guide
Your screen should now look like this:
XSEC ID:  BACKWATER <<
STAT
362
602
CHANNEL BANK STATIONS: 509.0 Right 605.0
MANNING'S 0.0650 Channel 0.0400 Right 0.0600
CHANNEL REACH LENGTHS:
LOSS 3000
WS ELEV
EG ELEV
F2}< Back Tab F5}PRINT F6}SAVE F7}Main Menu F8}New XSEC F10}Ed/Ex GrPt
TO BEGIN CALCULATIONS
The program is now ready to begin the calculations since all of the
required data has been entered for the 1st crosssection of our step
backwater analysis. Note that even at this point, if any of the data on the
screen has been typed in incorrectly, the user can simply press the
key to toggle backwards through all of the input data, even back to the
Ground Points. Remember that you can instantly go back to the Ground Points
by pressing , also.
13. Press to Begin the Calculations.
Your screen should now look like this:
XSEC ID:  BACKWATER <<
STAT
362
602
CHANNEL BANK STATIONS: 509.0 Right 605.0
MANNING'S 0.0650 Channel 0.0400 Right 0.0600
CHANNEL REACH LENGTHS:
LOSS 3000
WS ELEV 501.03 Depth 4.13 Top Wid 385 Kratio 1.00
EG ELEV 501.32 Flow Regime M1 ChanVel 5.10 Froud# 0.50
F2}< Back Tab F5}PRINT F6}SAVE F7}Main Menu F8}New XSEC F10}Ed/Ex GrPt
As you can see from the screen, the (100year) Water Surface Elevation (WS
ELEV) has been computed (501.03), with other variables.
413
StepBackwater Tutorial
>> STEP 0 POINTS GROUND
ELEV STAT ELEV STAT ELEV STAT ELEV
496.9 512 498.0 509 499.1 425 505.0
504.7 1020 500.1 732 498.2 605 496.9
Left
Left VALUES: N
Right Channel Left
:Dschrg Expansn COEFFICIENTS: Contractn
Kratio Top Wid Depth
Froud# ChanVel Flow Regime
Press
>> STEP 0 POINTS GROUND
ELEV STAT ELEV STAT ELEV STAT ELEV
496.9 512 498.0 509 499.1 425 505.0
504.7 1020 500.1 732 498.2 605 496.9
Left
Left VALUES: N
Right Channel Left
:Dschrg Expansn COEFFICIENTS: Contractn
Quick2 User's Guide page 414
QUICK2 User's Guide
Before we move on to enter the data for the next crosssection let's obtaina printout of this first calculation.
_ Press .
The screen prompt will be ...
PRINT: Summary or Detailed?
Let's obtain a Detailed Printout ... Therefore ...
_ Press D and then .
Assuming your printer is turned on, the detailed printout will look
this:
Cross Section:
XLOB: 0
NLOB:
STAT
362.00
602.00
CWSEL
Chan Vel
Depth
Discharge
501.03
5.10
4.13
3000
If any of the above variables are unfamiliar, a description of each isprovided in Appendix 1.
If you want to save the crosssection data to a different name and/ordirectory, before pressing , you can Press , F6}SAVE) toperform this.
Now we need to enter the data for the 2nd crosssection. Since we areentering a new crosssection (New XSEC), we need to ...
_ Press .
Before the Screen changes you will notice that at the bottom of the screena message will briefly appear ...
SAVING TEMPORARY FILE
This alerts you that your crosssection data has been saved to a filecalled T0.XSC, which is located in your C:\QUICK2\DATA directory.
414StepBackwater Tutorialand D or S Press
Press
like0CE: 0CC: 0 XROB: 0 XLCH: 0
.06NROB: 605 STCHR: .04 NCHL: 509 STCHL: .065
ELEVSTAT ELEV STAT ELEV STAT ELEV
512.00 496.90498.00 509.00 499.10 425.00 505.00
1020.00 504.70500.10 732.00 498.20 605.00 496.90
QROBQCH QLOB ELMIN EG
AROBACH ALOB KRATIO HV
STATRSTMIDCH STATL Top Width HL
FlowRegimEGSlope CHSlope Froude # OL
5052003 493 496.90 501.317
265392 228 1.00 0.29
789.9557.0 404.4 385 0.00
0.0029 0.0000 0.50 0.00
(,
C:\QUICK2\DATA\T0.XSC
QUICK2 User's Guide
StepBackwater Tutorial
Your screen should be blank again as shown below:
line
XSEC ID: 0 >> STEP  BACKWATER <<
GROUND POINTS
STAT ELEV STAT ELEV STAT ELEV STAT ELEV
Quick2 User's Guide page 415 a
Quick2 User's Guide page 415 b
Quick2 User's Guide page 415 c
Quick2 User's Guide page 415
CHANNEL BANK STATIONS:
MANNING'S
CHANNEL REACH LENGTHS:
LOSS
WS ELEV
EG ELEV
F2}<Back Tab F5}List Files F6}Retrieve File F7}Main Menu F10}Ed/Ex GrPt
F3}Insert GrPt F4}Delete GrPt F1 }HELP
_ Following the method used before, for the 1st crosssection, enter the
Ground Points one at a time, by their respective Station and Elevation for
the 2nd crosssection using the data provided. Be sure to Press
after you have typed in each correct number.
_ Once you have entered all of the Ground Points correctly, remember to
Press to Exit from entering Ground Point data .
_ Follow the on screen prompts to enter all of the other data.
Remember that if any of the data on the screen has been typed in
incorrectly, the user can simply press the key to toggle backwards
through all of the input data, even back to the Ground Points. (You can
also Press to go back to the Ground Points immediately for editing).
After entering all the data your screen should now look like this:
XSEC ID:  BACKWATER <<
STAT
0
331
CHANNEL BANK STATIONS: 233.0 Right 334.0
MANNING'S 0.0550 Channel 0.0400 Right 0.0600
CHANNEL REACH LENGTHS: 450 Channel 450 Right 450
LOSS 0.1 Expansn 0.3 :Dschrg 3000
WS ELEV
EG ELEV
F2}< Back Tab F5}PRINT F6}SAVE F7}Main Menu F8}New XSEC F10}Ed/Ex GrPt
TO BEGIN CALCULATIONS
Right Left
Right Channel Left VALUES: N
Right Channel Left
:Dschrg Expansn COEFFICIENTS: Contractn
Kratio Top Wid Depth
Froud# ChanVel Flow Regime
>> STEP 450 POINTS GROUND
ELEV STAT ELEV STAT ELEV STAT ELEV
500.9 236 502.2 233 504.8 150 510.0
510.1 591 505.5 402 501.8 334 500.9
Left
Left VALUES: N
Left
COEFFICIENTS: Contractn
Kratio Top Wid Depth
Froud# ChanVel Flow Regime
Press
415
QUICK2 User's Guide
StepBackwater Tutorial
The program is now ready to begin the calculations since all of the
required data has been entered for the 2nd crosssection of our step
backwater analysis.
_ Press to Begin the Calculations.
Once the calculation is finished you may ...
_
Press to obtain a printout
Press to save the data to another name and/or directory
_
Finally, to finish our analysis we need to enter in the data for the 3rd
crosssection.
_ Press
Before the Screen changes you will notice that at the bottom of the screen
a message will briefly appear ...
SAVING TEMPORARY FILE C:QUICK2\DATA\T450.XSC
This alerts you that your 2nd crosssection data has been saved to a file
called T450.XSC, which is located in your C:\QUICK2\DATA directory. Notice
that the 450, represents the channel distance between the 1st and 2nd
crosssections.
_ Following the method used before for the other crosssections, enter the
Ground Points one at a time, by their respective Station and Elevation for
the 3rd crosssection using the data provided. Be sure to Press
after you have typed in each correct number.
_ Once you have entered all of the Ground Points correctly, remember to
Press to Exit from entering Ground Point data .
_ Follow the on screen prompts to enter all of the other data.
After entering all the data for the 3rd crosssection ...
_
Press to Begin the Calculations.
Once the calculation is finished you may ...
_
Press to obtain a printout
Press to save the data to another name and/or directory
_
TO EXIT OUT OF THIS SCREEN NOW THAT OUR ANALYSIS IS COMPLETED ...
_ Press
416
QUICK2 User's Guide
StepBackwater Tutorial
You will see a screen prompt at the bottom ...
SUMMARY PRINTOUT: Press , otherwise Press
To print a summary of the output for all 3 crosssections then ...
_ Press , otherwise just Press
The on screen Summary or the printed summary will look like this:
SECNO Q XLCH CWSEL FR# ELMIN AVG.VEL. AREA TOPWID
0 3000.0 0 501.03 0.50 496.90 3.39 885.0 385.5
450 3000.0 450 503.96 1.06 500.90 7.54 398.1 196.9
940 3000.0 490 508.54 0.71 504.80 4.95 606.5 286.2
Quick2 User's Guide page 417
If we carefully compare the Computed Water Surface Elevations
(CWSELs) at each crosssection, to the topographic contours on
Figure 1, we will see that the property is clearly higher than
the CWSEL at every crosssection. Therefore this analysis with
more detailed crosssection data has proven that the property
has been inadvertently included in an unnumbered Zone A Special
Flood Hazard Area.
Turn to the next page to continue
417
QUICK2 User's Guide
StepBackwater Tutorial
RUNNING HEC2 USING QUICK2 FILES
{Tutorial Time: 5 minutes}
_ You will be prompted one more time to Press . The next prompt will
ask you a question concerning running the HEC2 or PLOT2 programs.
Press Y and to rerun w/HEC2 or PLOT2: If NO Press
_ For purposes of this tutorial let's answer "Y" , (and Press ) to
run the HEC2 program. The next screen that will appear will include the
following:
To Run

QUICK2
HEC2
AUTOHEC2
PLOT2
VIEW/PRINT
_ Type AH2 and Press .
Type
Q2
H2
AH2
P2
LIST
Quick2 User's Guide page 418
Once the HEC2 run is complete it will return you to the abovementioned
screen.
NOTE: Typing AH2 runs the HEC2 program automatically using the QUICK2
generated HEC2.DAT, HEC2 data file.
If you are using a HEC2 data file other than HEC2.DAT, then Type H2 and
Press . Follow the directions on the screen for naming the Input,
Output
_ Type LIST and Press , and then enter your output filename,
(Default is HEC2.OUT), to view the results. Note that you move up, down and
across the screen using the ,, the cursor keys, etc.
_ To Print the data that appears on the screen simply Press P.
_ To Exit from the screen simply Press X or the Escape key.
If you would like to complete the next tutorial example, then
Type Q2 and Press ; and, turn to the next page.
418
and Tape95 files; pressing after each filename is typed in.
QUICK2 User's Guide
StepBackwater Tutorial
RERUNNING USING SAVED CROSSSECTION FILES
{Tutorial Time: 5 minutes}
Let's say that in the analysis that was performed in the previous tutorial,
we want to change the discharge from 3000 to 5000, and run the step
backwater option again with the same crosssections. This is quite easily
done. Just follow the steps as shown below.
1. At the Main Menu Screen Type 4 and Press
2. At the Starting Water Surface Elevation Method Screen
Type .0029 and Press
3. At the Input/Output Screen Press to retrieve a saved cross
section file
Assuming your 1st crosssection file is stored as
C:\QUICK2\DATA\T0.XSC
Type C and Press when prompted for the directory
Type QUICK2\DATA & Press when prompted for the subdirectory
Type T0 and Press when prompted for the filename
4. Press to toggle back to the "Enter Discharge" prompt
5. Type 5000 and Press to enter the new discharge
6. Press to Begin the Calculations
7. Press to input another crosssection
Press to retrieve a saved crosssection file
Assuming your 2nd crosssection file is stored as
C:\QUICK2\DATA\T450.XSC
Type C and Press when prompted for the directory
Type QUICK2\DATA & Press when prompted for the subdirectory
Type T450 and Press when prompted for the filename
8. Press to toggle back to the "Enter Discharge" prompt
9. Type 5000 and Press to enter the new discharge
10. Press to Begin the Calculations
419
QUICK2 User's Guide
StepBackwater Tutorial
11. Press to input another crosssection
Press to retrieve a saved crosssection file
Assuming your 3rd crosssection file is stored as
C:\QUICK2\DATA\T940.XSC
Type C and Press when prompted for the directory
Type QUICK2\DATA & Press when prompted for the subdirectory
Type T940 and Press when prompted for the filename
12. Press to toggle back to the "Enter Discharge" prompt
13. Type 5000 and Press to enter the new discharge
14. Press to Begin the Calculations
_ Press to Exit out of the screen
_ Press to obtain a summary printout
_ Press twice to get back to the main menu
_ Press to leave the program
Q.E.D.
420
Quick2 User's Guide page 421
QUICK2 User's Guide
CHANNEL CAPACITY OPTION WITH THE RATING CURVE PLOT{Tutorial Time: 5 to 10 minutes}
Let's say that we need to determine a Base Flood Elevation (BFE) for theproperty shown in Figure 1. We do not want to exempt the entire propertyfrom the flood plain, only a structure which is located in the middle ofthe property. Therefore, we can use one crosssection (the 2nd cross
section (T450.XSC) from our previous tutorial and shown on Figure 1), tocompute a BFE.
Let's assume that we know the discharge is between 3000 cfs and 4000 cfsbased on our best estimates.
Let's assume our structure does not have a basement; the lowest adjacentgrade (LAG) to the house is at elevation 510 NGVD; and the first floorelevation (FFE) is 510.5 NGVD.
Let's determine the maximum carrying capacity of the floodplain using adepth equal to the lowest adjacent grade (510.0) minus the minimum streamelevation (500.9). For purposes of this example we'll use a depth of 9 feet(510501).
To perform a channel capacity calculation we also need to know thedownstream
information on page 15. Slope = 500.9  496.9 / 450 = .0089.
The graphic below sums up our situation so far:
””””””””””””””””””

____ ‹ FFE = 510.5
\ %‹ LAG = 510.0
\____ WSE = ? / ›
\/
\Q=3000  4000/ 9.1'
\/
\/___________fl____Stream Invert = 500.9
Slope = .0089
Follow the steps as shown on the next page to compute the rating curve...
421Channel Capacity Tutorialthefrom compute to easy is case this in which slope,
____
\/
Quick2 User's Guide page 422
QUICK2 User's Guide
1. At the Main Menu Screen Type 2 and Press
2. At the Shape of Cross Section Screen
Type I and Press
3. At the Input/Output Screen Press
We are using the 2nd crosssection file stored as
C:\QUICK2\DATA\T450.XSC
Type C and Press when prompted for the directory
Type QUICK2\DATA & Press when prompted for the subdirectory
Type T450 and Press when prompted for the filename4. Type .0089 and Press to enter the slope5. Type 9 and Press to enter the depth6. Press to Begin the Calculations7. Press to Plot to screen .... Press to PrintLooking at the rating curve plot we can see that for a discharge range ofbetween 3000cfs  4000cfs the BFE ranges from about 504.3 to 504.8. Sinceour lowest adjacent grade and first floor elevation are at or above 510, itis clear that this structure is above the BFE.
””””””””””””””””””

____ ‹ FFE = 510.5
\ ‹ LAG = 510.0
\____ WSE = 504.3504.8 / ›
\/
\Q=3000  4000/
\/
\/___________fl____Stream Invert = 500.9
Slope = .0089
8. Press to continue9. Press to go back to the Main Menu10. Press to Exit the program422Channel Capacity Tutorial____%
9.1'
QUICK2 User's Guide
PLOT2 Tutorial
PLOT2
In general PLOT2 will only work on QUICK2 files that have been converted into HEC2
format using QUICK2's StepBackwater option.
Profile plots from PLOT2 will work only if the QUICK2 generated data file (HEC2.DAT) is
also run using the HEC2 program (see Running HEC2 Using QUICK2 Files, page 418), since
a HEC2.T95 file needs to be generated by the HEC2 program for use by PLOT2.
PLOT2 Crosssection plots can be generated using the QUICK2 generated data file
(HEC2.DAT) even if it is not run with HEC2. However, the Crosssection plot will not show
the computed water surface elevation (CWSEL) unless the QUICK2 HEC2.DAT file is run with
HEC2, since the CWSEL is found on the HEC2.T95 file.
Note that the user can compute a normal depth elevation for only one crosssection and
have that crosssection plotted by choosing the StepBackwater option and the Normal Depth
starting water surface elevation method. Once the computation is finished, the user simply
exits (Presses ), and the QUICK2 program automatically creates the HEC2.DAT file for
that one crosssection, which can be used by the PLOT2 program.
Let's say that we want to view the water surface elevation profile and the
crosssection plots from our previous tutorial on the StepBackwater
option.
_ From the QUICK2 Title screen Press P2
_ You are now into the PLOT2 program, Press to continue
PROFILE PLOT {Tutorial Time: 5 to 10 minutes}
1. Let's view the profile first. Press 1 from the PLOT2 main menu
selection
2. Cursor to the HEC2 Tape95 file name entry and Type ?
This will list all of the data files in the QUICK2 directory. T95 files
are designated with the 3 letter extension .T95 . Therefore cursor over to
highlight that file (HEC2.T95) and Press .
3. Move up to highlight the Plot profiles entry and Press .
4. Your profile is now plotted. Pressing moves you back to the
Profile plots main menu screen. You can explore the different Profile and
Plotting options and replot the profile if you wish.
5. When you are finished plotting, highlight the Return to main menu
message and Press
423
QUICK2 User's Guide
PLOT2 Tutorial
CROSSSECTION PLOT {Tutorial Time: 5 to 10 minutes}
1. From the PLOT2 main menu Press 2 from the menu selection.
2. Cursor down to the HEC2 input file name entry and Type ?
This will list all of the data files in the QUICK2 directory. Input files
are designated with the 3 letter extension .DAT . Therefore cursor over to
highlight that file (HEC2.DAT) and Press . If we want to view a
different data file than that of the profile we previously viewed, we would
have to specify a different file here before proceeding.
3. Cursor down to the HEC2 Tape95 file name entry
Note that we do not have to reenter this file since we have already
entered it previously. If we want to view a different Tape95 file than that
of the profile we previously viewed, we would have to Type ?, and then
specify a different file here before proceeding.
4. Move up to highlight the Plot cross sections entry and Press .
5. You now have the option of printing all or selected cross sections from
your data file. Press Y for plotting all, or N for plotting selected cross
sections.
Your first crosssection is now plotted. Pressing moves you back to
the Crosssection plots main menu screen or plots additional crosssections
depending on how many crosssection plots you have. You can explore the
different Crosssection and Plotting options if you wish.
6. Highlight the Return to main menu message and Press
Pressing 4 at the PLOT2 main menu exits you from PLOT2 and back to the
QUICK2 title screen.
Note: To use PLOT2 and to access data files that are in another directory
(i.e., they are not in the C:\QUICK2 directory), just change to that data
directory (i.e., CD\dirname) and access PLOT2 by typing C:\QUICK2\PLOT2
(or A:\PLOT2 if using the program from the floppy drive) from that data
directory.
424
Chapter 5: FORMULAS
Critical Depth
Channel Capacity
Normal Depth
StepBackwater
Quick2 User's Guide page 51
51
QUICK2 User's Guide
Critical Depth Formulas
1. CRITICAL DEPTH
In every crosssection for a given discharge there exists a critical depth, where the
energy grade (depth of water plus velocity head  V2/2G) is at a minimum. Increasing the
discharge above this given discharge will force the flow into the supercritical regime.
Discharges below the given discharge will remain in the subcritical regime.
Supercritical depths will be lower than the critical depth, and subcritical depths will
be above the critical depth. Supercritical flow is characterized by small water depths
with large velocity heads; while, subcritical flow is characterized by large water depths
with small velocity heads. A rule of thumb used to determine critical depth is that when
the Velocity Head equals 1/2 the hydraulic depth (Area/Topwidth) critical flow is
probable.
A formula which can be used to approximate critical depth (D
c) is
given below.
Qc2 / g = A3 / T
Where Qc is the discharge (in cfs) based on critical depth, g is the gravitational
constant (32.15 feet/second squared), A is the crosssection area (in square feet), and T
is the top width of the water surface (in feet). Note: for rectangular channels the above
equation can be reduced so that
D = (Qc/5.67 T).667.
c
The more exact way to compute critical depth (minimum specific energy) is to find a
specific depth of water within a crosssection for a given discharge which produces the
lowest energy grade. The following represents the process that the Critical Depth option
of QUICK2 goes through to calculate critical depth.
After the crosssection information (ground points, channel stations, etc.) has been input
the program starts computing the water surface elevation (WSE) and corresponding energy
grade elevation (EG) at a depth of 0.1 foot above the lowest elevation in the
crosssection. It continues to calculate WSE and EG at intervals of 0.5 foot. As the depth
of water in the crosssection increases the EG will decrease. At one point the EG will
begin to increase. This means that between the last 0.5 foot interval there exists a
minimum energy grade. Once this has occurred the program decreases the WSE in intervals of
.02 foot. As the depth of water decreases in the crosssection the EG will also decrease
as it approaches the minimum specific energy. At one point the EG will begin to increase
again.
This means that between the last .02 foot interval critical depth exists. At this point
the screen will display the actual critical water surface elevation (along with other
variables) by assuming that the next to the last iteration was the critical depth.
The calculations performed by the program for a given crosssection are listed on the next
page. The calculations include the iterations that the program goes through to arrive at
critical depth.
52
QUICK2 User's Guide
Critical Depth Formulas
ELMIN = 92.5
WSE = 92.6 Qc= 6.026845E02 Q= 260 EG=466080.8 EG Decreasing
WSE= 93.1 Qc= 5.314738 Q= 260 EG=452.6406 
WSE= 93.6 Qc= 24.18726 Q= 260 EG=125.4259 
WSE= 94.1 Qc= 61.71717 Q= 260 EG=101.21 
WSE= 94.6 Qc= 121.451 Q= 260 EG=96.99928 
WSE= 95.1 Qc= 204.4488 Q= 260 EG=96.14474 v
WSE= 95.6 Qc= 311.15 Q= 260 EG=96.14897 + EG Increasing
Therefore Minimum Specific Energy is between WSE's of 95.1 and 95.6. Note also that the
Discharge (Q = 260) is also within the computed Critical Discharge (Qc) range of 204 
311.
WSE= 95.58 Qc= 306.5006 Q= 260 EG=96.14179  EG Decreasing
WSE= 95.56 Qc= 301.8821 Q= 260 EG=96.13499 
WSE= 95.54 Qc= 297.2962 Q= 260 EG=96.12863 
WSE= 95.52 Qc= 292.7447 Q= 260 EG=96.12271 
WSE= 95.50 Qc= 288.2256 Q= 260 EG=96.11724 
WSE= 95.48 Qc= 283.737 Q= 260 EG=96.11225 
WSE= 95.46 Qc= 279.2825 Q= 260 EG=96.10776 
WSE= 95.44 Qc= 274.8583 Q= 260 EG=96.1038 v
WSE= 95.42 Qc= 270.4678 Q= 260 EG=96.10038 
WSE= 95.40 Qc= 266.1075 Q= 260 EG=96.09752 
WSE= 95.38 Qc= 261.7806 Q= 260 EG=96.09525 
WSE= 95.36 Qc= 257.4854 Q= 260 EG=96.09361 
WSE= 95.34 Qc= 253.22 Q= 260 EG=96.09262 
WSE= 95.32 Qc= 248.986 Q= 260 EG=96.09199 minimum v
WSE= 95.30 Qc= 244.76 Q= 260 EG=96.09271 + EG Increasing
We assume that ... Critical Depth = 95.32', Minimum Specific Energy = 96.09199'
The Froude number would be, Q / Qc, or 260 / 248.986 = 1.04.
It is not unusual for the Froude number to not equal exactly 1.0, since the calculation of
critical discharge using the formula Qc2 / g = A3
is exactly at the True minimum specific energy.
/ T, does not always yield a WSE that
You should notice from the above tabulation, that as you approach critical depth (minimum
specific energy), for very small changes in EG there are large jumps in the water surface
elevation. The EG is only changing by .001' to .003' while the WSE changes by .02'. A
0.01' difference in EG can cause a 0.10' change in WSE.
53
QUICK2 User's Guide
Channel Capacity Formulas
2. CHANNEL CAPACITY
In this option, a Normal Depth elevation (see 3. NORMAL DEPTH) is input and the program
computes the corresponding discharge. (In the Normal Depth option, the discharge is input
and the program computes a normal depth elevation). The Manning's equation is used as the
formula for determining the (normal) discharge.
Q = 1.486 A (R.667) S.5 / N
Where Q is the discharge (in cfs), A is the crosssection area (in square feet), R is the
hydraulic radius (in feet), S is the energy slope (in feet/feet), and N is the Manning's
roughness value.
After the crosssection information (ground points, channel stations, streambed slope,
normal depth elevation(s), etc.) has been input, the program simply solves for the area
(A) and hydraulic radius (R) below the normal depth elevation (specified by the user) and
computes the (normal) discharge directly using the Manning's equation. This is not an
iterative process. The screen will display the (normal) discharge (which represents the
channel capacity) along with other variables.
54
QUICK2 User's Guide
Normal Depth Formulas
3. NORMAL DEPTH
The standard formula for determining normal depth in a crosssection is the Manning's
formula. Water is flowing at normal depth when the energy grade and the hydraulic grade
(water surface) slopes are the same as the stream bed slope. Normal depth profiles occur,
in general, when the flow is uniform, steady, onedimensional, and is not affected by
downstream obstructions or flow changes. The standard Manning's equation is:
Q = 1.486 A (R.667) S.5 /N
Where Q is the discharge (in cfs), A is the crosssection area (in square feet), R is the
hydraulic radius (in feet), S is the energy slope (in feet/feet), and N is the Manning's
roughness value.
The exact method for computing normal depth for a given discharge at a particular
crosssection, is to assume that S is equal to the downstream streambed slope and to solve
iteratively for the depth (this obviously assumes N is known). The following represents
the process that the Normal Depth option of QUICK2 goes through to calculate normal
depth.
After the crosssection information (ground points, channel stations, discharge, streambed
slope, etc.) has been input, the program starts computing discharge using the Manning's
equation at an initial depth of 0.1 foot above the lowest point in the crosssection, and
from that point in 0.5 foot intervals. At some point, the computed discharge will exceed
the given target discharge. The program then uses a converging technique to compute a
discharge (with a corresponding normal depth) that is within 1% of the given discharge. At
this point the screen will display the actual normal depth water surface elevation (along
with other variables).
The calculations performed by the program for a given crosssection are listed below. The
calculations include the iterations that the program goes through to arrive at normal
depth.
ELMIN= 92.5
WSE = 92.6 Q= 260 Computed Q= .023579
WSE= 93.1 Q= 260 Computed Q= 2.803083
WSE= 93.6 Q= 260 Computed Q= 14.11313
WSE= 94.1 Q= 260 Computed Q= 38.33264
WSE= 94.6 Q= 260 Computed Q= 80.01045
WSE= 95.1 Q= 260 Computed Q= 146.9773
WSE= 95.6 Q= 260 Computed Q= 245.9516
WSE= 96.1 Q= 260 Computed Q= 369.2461
WSE= 95.65697 Q= 260 Computed Q= 258.7531
below target Q
below
below
below
below
below
below
above target Q
within 1%
We assume that ... Normal depth = 95.66 for a Discharge (Q) of 260 cfs
55
QUICK2 User's Guide
StepBackwater Formulas
4. STEPBACKWATER
The Energy Equation which represents onedimensional, uniform, and steady flow in open
channels is shown below.
(1) WSEd + HVd = WSEu + HVu + HL + OL
Where WSEd is the water surface elevation at the downstream crosssection, HVd is the
velocity head at the downstream crosssection, WSEu is the water surface elevation at the
upstream crosssection, HVu is the velocity head at the upstream crosssection, HL is the
friction loss between the two crosssections, and OL is the eddy (contraction or
expansion) loss between the two crosssections.
Velocity Head, HV, is calculated as follows:
HV = (a) V2 / 2g
Where (a) is alpha the velocity coefficient, V is velocity (Q/A), and g is the
gravitational constant. Alpha (a) is calculated as follows:
(A2) Kl3 Kc3 Kr3 
(a) =  +  + 
(K3) Al2 Ac2 Ar2 
Where A and K are the total area and conveyance below the water surface, respectively; and
Kl, Kc, Kr and Al, Ac, Ar, are the conveyance and area in the left overbank, channel, and
right overbank, respectively.
Friction Loss, HL, is calculated as follows:
HL = Lw ( Qd + Qu )2 / ( Kd + Ku )2
Where Lw is the discharge weighted reach length between cross sections, Qd is the
discharge at the downstream crosssection, Qu is the discharge at the upstream cross
section, Kd is the conveyance at the downstream crosssection, and Ku is the conveyance
at the upstream crosssection. This is derived from the Average Conveyance Friction slope
equation.
The Discharge Weighted Reach Length, Lw, is calculated as follows:
Lw = {(Ll * Ql) + (Lc * Qc) + (Lr * Qr)} / Qa
Where Qa is the average total discharge between crosssections; and, Ll, Lc, Lr, and Ql,
Qc, Qr, represent the reach length and average discharge between crosssections for the
left overbank, channel, and right overbank, respectively.
Eddy Loss, OL, is calculated as follows:
OL = (Ce or Cc) * ABS HVd HVu
Where Ce is the expansion coefficient, Cc is the contraction coefficient, HVd is the
velocity head at the downstream crosssection, and HVu is the velocity head at the
upstream crosssection. When HVu is greater than HVd Ce is utilized. When HVu is greater
than or equal to HVd Cc is utilized.
56
QUICK2 User's Guide
StepBackwater Formulas
After the crosssection information for the first crosssection has been input, either a
known water surface elevation is input to start the calculations or the water surface
elevation could have been determined by the Normal or Critical Depth options or by another
source or method. The program then computes all pertinent variables for the first
crosssection that will be needed for an energy balance with the next upstream
crosssection. After this the user must put in the appropriate information for the next
crosssection (i.e., ground points, channel stations, reach lengths, contraction and
expansion coefficients, etc.). Once this is done the program performs a series of trial
iterations to make sure that the Energy Equation (1) listed previously will balance to
within .014 foot. The sequence of trial elevations is listed below.
1ST TRIAL:
Uses the depth of water (DP) of the previous crosssection added to the lowest elevation
(ELMIN) within the current crosssection. If DP + ELMIN is less than the previous WSE
(i.e., adverse slope condition) then the program uses the previous WSE for the 1st trial
at the current crosssection.
2ND TRIAL:
Uses the average of the computed WSE and the WSE assumed in Trial number 1.
3RD TRIAL AND ON ...:
Uses a formula designed to help converge quickly to balance the energy equation as shown
below:
Trial WSE = WSE(WSE+HVDGHLOL)/(1((Q/QC)2)+((1.5*HL)/(A/W)))
Where WSE, HV, HL, OL, QC, A, and W are the latest computations of water surface
elevation, velocity head, friction loss, eddy loss, critical discharge, total area, and
total wetted perimeter, respectively; and, DG is the computed energy grade elevation from
the previous crosssection; and, Q is the discharge at the current crosssection.
For most energy balances between crosssections that are not at or near critical flow, the
program will balance the energy equation within 5 trials.
The calculations performed by the program for an energy balance between two crosssections
are listed below. The calculations include the iterations that the program goes through to
arrive at the energy balance.
WSE WSE
Assumed Calculated Difference Trial #
98.75 98.32489 +.4251099 1
98.53744 98.32472 +.2127228 2
98.32476 98.32513 .00037 3
We assume that the correct WSE = 98.32
Note: Energy balance in this case was accurate to .00037 foot.
57
QUICK2 User's Guide
Definition of Variables
Appendix 1: Definition of Variables
ACH Area within the specified channel below the water surface elevation
ALOB Area within the specified left overbank below the water surface elevation
AROB Area within the specified right overbank below the water surface elevation
ALPHA  Velocity head coefficient
AREA or Area  Total area within the crosssection below the water surface elevation
AVG.VEL or Velocity  Average Velocity within the entire crosssection
Base Width  Channel bottom width of a trapezoidal or rectangular crosssection
Bottom Width  Channel bottom width of a trapezoidal or rectangular crosssection
CC  Contraction Coefficient
CE  Expansion Coefficient
CHSLOPE  Slope of the streambed, Channel Slope
CHANVEL or ChanVel  Velocity within the main channel of crosssection
Critical Slope  Slope of the Energy Grade line at Critical Flow
CWSEL  Computed water surface elevation within a crosssection
Depth  Max depth of water in the crosssect as measured below the water surface elevation
Diameter  Width or Height of a circular pipe
Discharge  The rate of the flow of a volume of water within a crosssection, usually
expressed in cubic feet per second (cfs)
EG or EG ELEV  Energy grade elevation, expressed as, WSE + HV
EGSlope  Energy grade slope
ELEV  Elev of a ground pt of a crosssect, as ref to some datum (i.e., NGVD, NAVD, etc.)
ELMIN  Lowest elevation in a cross section
Flow Regime  Type of water surface profile (Supercritical regimes are not computed)
M1: EGSlope <= ChSlope and FR# < .8 M2: EGSlope > ChSlope and FR# < .8
C1: EGSlope <= ChSlope and FR# >= .8 C3: EGSlope > ChSlope and FR# >= .8
Flow Type  either, Supercritical, Critical or Subcritical
Froude#, Froude No., Froud# or FR# Froude number, used to determine the flow type
(i.e., sub (FR# < 1), critical (FR# = 1) or supercritical (FR# > 1) flow)
HL  Friction loss between cross sections
HV  Velocity head
Hyd Radius or Hyd R Hydraulic Radius: equal to (Area / Wet Perimeter)
A1
QUICK2 User's Guide
Definition of Variables
KRATIO  Ratio of upstream total conveyance to downstream total conveyance
L Side Slope  Ratio of the slope of the left side of a channel in terms of Horizontal
distance in feet to 1 foot Vertical.
Manning's n  Coefficient used to account for the friction caused by earthen, vegetative,
and/or manmade surfaces within a floodplain crosssection.
Max Discharge  The maximum flow possible within a circular pipe, (usually occurring at
.94 * Diameter).
NCHL, NLOB, NROB  Manning's "N" value for the specified channel, left overbank, and right
overbank, respectively.
OL  Expansion/contraction loss
Q  Total discharge in the crosssection
QC  Critical discharge within entire crosssection for a specific water surface elevation
QCH  Discharge within the specified channel of a crosssection
QIC  Critical discharge within the entire crosssection for a specific water surface
elevation, assuming that critical flow is limited to the channel, even if flow is
occurring in the overbanks
QLOB, QROB Discharge within the specified left overbank, and right overbank,
respectively, of a crosssection
R Side Slope  Ratio of the slope of the right side of a channel in terms of Horizontal
distance in feet to 1 foot Vertical.
SECNO  Cross section number or identifier
Slope or EGSlope  Energy grade slope
STATL, STATR  Station, within a crosssection, of the left edge, and right edge,
respectively, of the water surface
STAT  Station of a ground point of a crosssection
STCHL, STCHR, STMIDCH Station of the left bank, right bank, and midpoint,
respectively, of a crosssection
Top Width or Top Wid  Top width of the water surface within a crosssection
Velocity  Average Velocity within the entire crosssection
Wet Perimeter or Wet Per  actual width of ground within a crosssection below the water
surface elevation.
WS ELEV or CWSEL  Water surface elevation within a crosssection
XLCH, XLOB, XROB  Distance between crosssections as measured along the channel, left
overbank, and right overbank, respectively.
A2
NOTES