United States Department of Agriculture
Natural Resources Conservation Service
POND
Pond Design with Storage Indication Routing
Version 2.01
March 2001
written by:
Clinton W. Liezert PE
Civil Engineer
E-34669
POND.EXE
Version 2.0
Table of Contents
Introduction ..............................................................................................................................1
Supporting Files ......................................................................................................................2
Loading POND ........................................................................................................................3
Main Menu ...............................................................................................................................3
Design Options ........................................................................................................................3
Stage-Storage Information .....................................................................................3
Hydrology options ....................................................................................................4
Entering watershed data ...........................................................................4
Inputting hydrograph coordinates..........................................................6
Material Selection ....................................................................................................6
Computing Elevations.............................................................................................7
Hydrograph Plots .......................................................................................9
Data File Management ..........................................................................................................9
Retrieving Data .........................................................................................................9
Saving Data ................................................................................................................10
Removing Data Files ...............................................................................................10
Options ......................................................................................................................................10
Clear Memory............................................................................................................10
Inputting Discharge Rating Data..........................................................................11
Modifying parameters and default values .........................................................11
Program Details ........................................................................................................12
Switching active printers ........................................................................................12
Temporary exit to DOS ..........................................................................................12
Quitting POND........................................................................................................................13
Technical Information ...........................................................................................................13
Format of saved data ...............................................................................................13
Pipe tables ..................................................................................................................14
Design details ............................................................................................................16
Appendix P
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POND.EXE
Version 2.0
Introduction:
The pond program was designed to deal with the complete design of small to
medium sized water impoundments as well as to evaluate the design of large existing
facilities. The program has a great deal of diversity and provides many options related to
designing and evaluating ponds. The features include:

Development of a stage - storage curve or relationship.

Develop hydrology internally (frequency and maximum probability).
Accept an inflow hydrograph from other sources.
Consider a variety of spillway types and materials.
Develop a stage - discharge relationship internally.
Accept a stage - discharge relationship from other sources.
Route hydrographs through structures using storage indication methods.
Provides warnings where designs might be considered inefficient or in
conflict with design standards or state law.






In this approach to pond design, the principal and emergency spillway systems are
presumed (guessed at) and the design storms are applied to the system. The elevations
related to this system are calculated and displayed. If the results are not acceptable to the
designer, the spillway systems are modified and the system is routed again. This process is
repeated until the results are satisfactory.
Appendix P
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POND.EXE
Version 2.0
Supporting Files:
The pond design program is contained in a file called "POND.EXE". In order to
run, it must be supported by several additional files on the default drive. They are:
BRT71EFR.EXE
This is a runtime module that is copyrighted to
Microsoft Quick BASIC 
OH_ENG.CFG
The file containing all of the specifics about your
computing system such as type of printer.
CLIMATE.DAT
A data file that contains the rainfall information.
This file is constructed in a format that requires a
special editor (CLIM_ED) to modify. Do not attempt
to change it with any other editor. Without this file,
rainfall information can not be retrieved and that
information will need to be manually entered.
POND.STD
This file contains the default values or any standard
values that may apply to this program. Normally this
file contains information that is managed from within
the POND program. (''modify parameters")
POND.ST2
A file that contains many default values and controls
that the program uses. This is an ASCII file that can
be modified although it is not highly recommended.
POND.HLP
A file that contains the help information for this
program. The program will run without this file but
there will obviously be no help information available
and a file with this name that contains no data will be
created.
PIPES.PND
Contains the types of pipe materials and associated
"n" values that are available to the program. Should
additional materials become available, they can easily
be added to the system. Just be certain that the
structure of the file is maintained.
DIMHYD.DAT
A file that defines the dimensionless hydrograph.
The information is this file is necessary for the
hydrograph development routine.
RAIN*.DAT
There is a table for each of the rainfall distributions
that are available. Each file contains the data
definition of the associated distribution pattern.
Appendix P
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POND.EXE
Version 2.0
Loading POND:
"POND" can be loaded in one of two ways. Make certain that you are in the
subdirectory where the engineering programs reside. The main "Ohio Engineering
Menu" can be loaded first by entering "ENGMENU" at the DOS prompt ( C> ) and then
selecting the "Pond Design" program from the choice list. The second option is to simply
enter "POND" at the DOS prompt.
POND Main Menu -
Design

Files
Options
Quit
When the program is first activated, a menu similar to that above will be displayed.
The marker identifies the function that is currently active. Pressing "F1" will display a
small description of the function. Pressing "Enter" () or the left mouse button will
activate the current function, and display a list of options available under that function.
The first letter can also be used to activate any of the specific selections. The right and left
arrow keys or the mouse can be used to move the marker.
Design Options:
Design
║
Files
Options
Quit
Stage-Storage Calculations
Hydrology
Material Selection
Compute Elevations
Stage-Storage Calculations:
In order to calculate a storage indication routing, the storage capabilities of the
structure needs to be known at various elevations. This portion of the program provides
the tools to develop this information.
The first entry requests the elevation at the lowest point along the centerline of the
dam. This information is used as a starting point for the structure as well as being
instrumental in determining the design criteria. Subsequent lines will request an elevation
and the area of the water surface at that elevation. Fifteen entry lines are available. It is
not necessary that all of the lines be used but the better the site is defined, the better the
final results. At least one line of information above the final water elevation is required.
As the elevation and area flooded are entered, the accumulative storage is calculated.
The first calculation is based on 0.4 x elevation difference x sum of areas. All subsequent
calculations are based on 0.5 x elevation difference x sum of areas. Several publications
Appendix P
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POND.EXE
Version 2.0
uses this procedure to account for the unevenness that typically exists along the bottom of
the pond. This is pointed out so that you can make necessary adjustments if they are
appropriate.
Should the accumulated storage column display as series of asterisks (*******), it is
an indication that you have entered bad data. Either the elevation is less that the previous
line or the area flood area is smaller than that on the previous line.
When this screen is complete, you can either return to the main menu or press PgDn to
go to the hydrology screen. PgDn will direct you to the standard hydrology procedures but
it will not offer all of the hydrology procedures that are available from the main menu.
Hydrology:
Design
║
Files
Options
Quit
Stage-Storage Calculations
Hydrology
Material Selection
Compute Elevations
Enter Watershed Data
Input Hydrograph Coords
Enter Watershed Data:
Two methods are available for inputting the hydrology into the system. The first
involves entering the watershed characteristics and relying on the program to develop the
hydrology. This is the first selection on the menu. When this option is selected, a data
form will appear on the screen. The following discussion is related to the questions that
are asked on this form.
Job:
Landowner - enter the name of the person that owns the pond
site. This is the name that will appear on the printed
reports for the completed design.
County - this should be the county where the pond site is
located. By entering the county name (and spelling it
correctly) the rainfall amounts that are required will be
automatically retrieved.
Designed by - this should be the name or initials of the person
that is to receive the nice plaque for design such a nice
pond. It is also the name of the person who will sign the
check if the pond washes out.
Watershed:
Drainage Area (acres) - enter the number of acres involved in
the area that sheds water to the pond site. This values is
required in order to classify the structure and well as to
complete the design.
Appendix P
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POND.EXE
Version 2.0
Runoff Curve Number - this number represents the ability of the
watershed to convert rainfall to runoff. The procedure for
developing this number is covered in several pieces of
literature including the National Engineering Field
Handbook of the Natural Resource Conservation Service
(NRCS).
Watershed Length - this value should represent length of the
path that would require the most time for a drop of water to
travel across the watershed to the pond site.
Average Watershed Slope (%) - enter the average slope of the
watershed in percent (ft / 100 ft.). This value should
represent the entire watershed area and not just the path
that the water takes.
Time of Concentration (hrs) - once the above numbers have
been entered, this value should be automatically calculated.
If you by chance come up with a better value using another
method, you can overwrite the calculated value with your
own.
Principal Spillway:
Design Frequency - enter the storm event frequency that should
be used for the design of the principal spillway system.
Most often this entry will default based on information that
was previously entered.
xx yr. - 24 hr rainfall (in) - this entry represents the rainfall
amount that is associated with the frequency that was
entered on the previous line. If the county was properly
identified, this value should be automatically retrieved.
Design Discharge (cfs) - if the previous values on this screen
are complete and appropriate, this value will automatically
be calculated. The computation involves the generation of
all of the coordinates of the inflow hydrograph. This might
take a few seconds if you are using a computer with an
older processor.
Emergency Spillway: Design Frequency - this frequency represents the statistical
number of years that are acceptable between times that the
emergency spillway experiences flow.
xx yr. - 24 hr rainfall (in) - the rainfall associated with the
frequency entered on the previous line.
Design Discharge (cfs) - as before, this value will be calculated
automatically when all of the data is available.
(option where design Percent of Max Probable Precip - if the design is to be base on a
is based on PMP)
probable maximum analysis (determined within modify
parameters), this entry indicated the percent of the probable
Appendix P
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POND.EXE
Version 2.0
maximum precipitation should be used in the emergency
spillway design.
Maximum Probable Precip (in) - the maximum probable
precipitation for the area where the pond is located. Once
again, this value should be automatically retrieved.
Design Discharge (cfs) - the design discharge for the emergency
spillway will be calculated automatically.
Rainfall Type:
Rainfall type refers to the distribution of rainfall that normally
occur in the area involved. This value is usually I, IA, II or
III. In Ohio and the majority of the US a value of II should
be used. Further information can be found in Section IV of
the NRCS National Engineering Handbook or Chapter 2 of
the NRCS National Engineering Field Handbook.
Input Hydrograph Coords:
The other method of providing hydrology information is to enter the coordinates of the
hydrograph manually. This hydrograph information normally will come from another
source such as stream gage records that record the actual discharges for specific storms,
TR20 (project formulation) computer runs, etc.
A form will appear to be filled in that defines the inflow hydrographs that are to be
used to route the principal and emergency spillway events. The following information will
be requested:
Watershed drainage area - enter the number of acres that drain to the pond site.
Time in hours - break the hydrograph into units of time that will best define the
shape of the hydrograph. Times that define the straight sections of the
hydrograph can be longer than those that define the curved portions.
Principal Inflow - reading from the principal spillway inflow hydrograph, enter the
discharge in cubic feet per second (cfs) that is associated with the time on this
particular line
Emergency Inflow - do the same for this entry as before except read from the
emergency spillway inflow hydrograph.
Material Selection:
Using this selection, information about the spillway systems is entered.
Type of Principal Spillway - Pressing F4 will cause a list of the types of spillway
system that can be analyzed by the program. If the desired type does not exist, a rating
curve for the type you prefer can be entered. This procedure will be covered later.
Principal Spillway Materials - F4 will provide a list of the materials, and the associated
"n" values, that are available to the system.
Appendix P
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POND.EXE
Version 2.0
Emergency Spillway Retardance - Once again, F4 will provide a list of values that the
program uses. Information related to retardance can be found in the (NRCS) National
Engineering Handbook. Basically the retardance reflects the resistance to flow in the
emergency spillway because of the grass. "D" would typically be used in conditions where
one could expect good maintenance (frequent mowing) in the emergency. If the grass is
allowed to pretty much go wild, a "B" retardance would likely be used.
Compute Elevations:
This is where all of the action is in the POND program. A form will appear that
contains much of the information about the pond. Several of the items will be "seeded"
with information that is typically used for pond designs. There are also several special
purpose keys that are available on this screen.
As discussed earlier, the philosophy of this program is to estimate (or guess) a pond
system and compute the resulting elevations. If the resulting elevations are unacceptable,
adjust the properties of the pond system accordingly and recompute. It is much the same as
the way in which the son of an SCS engineer described his dad's work to his grade school
class. He said "My dad builds dams and then stands back to watch how high the water
gets." This is pretty much how the program works.
The following information will be listed on the form:
Waterline Elevation - This is the elevation of permanent water or the pool
elevation. It is the elevation at which water begins to flow through the spillway
system.
Principal Spillway Outlet Elevation - Enter the elevation of the flow line (invert) at
the outlet end of the principal spillway pipe. The program uses this information
to compute the head or water pressure on the spillway system.
Invert of Pipe @ jct w/ Riser - This is the flowline elevation of the principal
spillway (horizontal) pipe at the point where it joins the riser (vertical) pipe. As
you might expect, this question information will not be requested if a hooded
inlet or bleeder pipe spillway system was selected earlier.
Principal Spillway Diameter (in) - Enter the diameter of the principal spillway
(barrel) in inches. This is the diameter that you would prefer to use. It is wise
to be certain that the size you select is manufactured in the material that was
selected earlier.
Riser Diameter (in) - Initially, a size will be displayed that is compatible with the
size of the spillway system that was selected. This initial value will normally
provide a combination of riser and pipe that is hydraulically efficient. If you
don't like the size that initially appears, change it with a willingness to accept
the consequences.
Emergency Spillway Width (ft) - Enter the preferred width of the emergency
spillway. This width should be measured within the level (control section)
portion of the emergency.
Appendix P
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POND.EXE
Version 2.0
Top Width of Dam (ft) - Enter the desired top width of the embankment. The
program will start with a number that is based on the height of the dam, but you
are free to change it.
Width of Upstream Berm (ft) - It is common to construct a berm across the
upstream side of a dam to help deal with wave action. On some occassions, a
semi-circular berm is constructed around the riser to help support it. In either
case, the dimension of this berm is entered here and it's width affects the length
of the spillway system.
Freeboard (ft) - This is a safety factor that is included in pond design and represents
the distance between the elevation in the pool when the emergency spillway is
flowing at design depth and the elevation of the top of dam. This value is
usually tied to a design standard.
Upstream Sideslope - This is the slope ratio of the upstream (water side) surface to
the embankment. It is expressed in feet of run per foot of rise. For example,
3:1 infers that there will be one foot of elevation for each three feet horizontally.
Downstream Sideslope - This is the same definition as above except that it relates
to the downstream side of the embankment.
When the form has been completed, the computation can be done. This process is
activated by pressing the F9 key. As the process proceeds, several messages will be
displayed indicating the progress of the calculations. On some of the newer computers,
these messages may not appear long enough to read, so for those with computers with
"blazing" speed, the following things are being done. The program will begin by building
the data sets that are required for the routings. It will then route the principal spillway
storm event and set the elevation of the emergency spillway. Then the emergency spillway
storm will be routed to determine the depth of flow in the emergency spillway. Freeboard
will be added to set the top of dam elevation.
As part of the design process, the program has to make a few assumptions to
determine the actual length of the pipe that is involved in the spillway. The routings are all
done based on this assumed pipe length. Once the elevations have been determined by the
routings, the length of pipe can be calculated with more assurance. If there is a significant
discrepancy between the length that was computed and the length that was assumed, the
difference will be displayed and you will be asked if you would like to recalculate the
design based on the new length. You will have to decide how much variation you want to
accept in your designs.
When the design has been completed, there may be another message appear that
identifies some conditions related to the design. For example, you might be told that this
project might fall within state regulations, or the weir is controlling and a larger riser might
result in a more efficient design, or several other tidbits of information. The program is not
affected by these statements. They are presented for information only and you are the only
one that can react to them.
Once the computations are complete and the results are displayed on the screen, there
are two key stroke combinations that might be of interest.
Alt P - will cause the inflow and outflow hydrographs for the principal spillway
routings to be displayed on the screen.
Appendix P
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POND.EXE
Version 2.0
Alt E - will cause the inflow and outflow hydrographs for the emergency spillway
routings to be displayed on the screen. (See the plot below.)
Alt P - while the plots are on the screen, will cause the hydrograph plots to be
printed on the printer.
Data File Management:
Design
Files
Options
Quit
º
Get a Job
Save a Job
Remove a Job
Get a job:
This feature allows you retrieve data that has been stored or saved on previous
occasions by this program (POND). You will be shown a list of the data files that
are available on the default drive. If your data is on a different drive or in a
different subdirectory than the default, pressing Alt C will afford you an
Appendix P
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POND.EXE
Version 2.0
opportunity to select an alternative drive and a new list will appear. Cursor to the
job that is desired and press return () and the data will be retrieved.
Save a job:
This selection will provide the information required to save the data for the job
that is currently in computer memory. It is wise to visit this area frequently while a
large job is being entered so that portions of your work is not lost. You never can
tell when the lights might go out or someone might accidentally hit the reset button.
A screen will appear that identifies the data that is to be saved. Refer to the
main guide for the Ohio Engineering programs for discussion related to the file
naming procedures and assistance related to the information that is requested on
this screen. The code used to identify POND data in the file naming scenario is
"PND".
Remove a job:
Many of us do not like to throw anything away but occasionally reality sets in
and we concede to the need. There might be test jobs, old jobs or jobs that you
don't want the boss to see that should be removed from the system. This selection
works in a similar manner to retrieving data files. Once the desired file has been
selected, you will be asked to confirm your request.
It is desirable to remove data files using this procedure rather than simply
erasing them with DOS commands. This procedure also will properly manage
other related files that the DOS procedures do not know about..
Options:
Design
Files
Options
Quit
º
Clear Memory
Input Discharge/Rating Data
Modify Parameters
Program Details
Switch Printers
Temporary Exit to DOS
Clear memory:
If you get to the point that you have things so messed up that you would like to
start over, this is the routine to use. It will give you a fresh start. Everything
previously in memory will be gone after this operation. If there is a chance that you
may change your mind, it might be wise to save the data before proceeding with
this option.
Appendix P
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POND.EXE
Version 2.0
Input Discharge/Rating Data:
There may be occasions when it is desirable to design or evaluate a pond or
structure that has a spillway other than a pipe system or one that has a unique pipe
system. This option provides the means of entering stage-discharge information for
nearly any type of spillway that you can imagine. Basically, if you can determine
the hydraulic capabilities of a spillway system at a variety of elevations, that
spillway can be considered in a pond.
Upon selecting this process, a data entry form will appear in which you enter
elevations with respective discharges. Begin the data at the normal waterlevel in
the pond and try to provide enough information to cover the storm events that the
pond will be subjected to.
Modify Parameters:
A screen will appear with several items of information that are used within the
program. Several of them appear as default values. The following items relate to
this screen.
Top width of dam (ft) - enter the value that is typically used at your location.
Width of berm at waterline (ft) - the value will be used as a default.
Upstream sideslope - the value will be used as a default.
Downstream sideslope - the value will be used as a default.
Length of pipe extending beyond dike (ft) - this value relates to the amount
of pipe that extends beyond the point where the principal spillway pipe
intersects the downstream sideslope of the embankment. Over the
years we have used a value like six (6) feet, but this value might
change from site to site.
Length of riser extending below pipe - enter the amount of riser that extends
below the point where the principal pipe (horizontal portion) connects
to the riser. This is the portion that is typically filled with concrete to
act as ballast. Once again, this value might change from site to site.
Position of riser - pressing F4 will provide choice list outling several
variations of placing the riser. This affects the computation of pipe
lengths.
Type of Principal Spillway - press F4 and select the typical spillway type
that is used in your office.
Principal Spillway Materials - use F4 and select a default material for the
typical pond in your office.
Emergency Spillway Retardance - the default retardance.
Should the emergency design be based on a frequency or a percent of
probable maximum precipitation (F/P) - most ponds or structures that
Appendix P
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POND.EXE
Version 2.0
are built under NRCS standard 378 are based on a "frequency" type
storm, such as a 10 yr.or 25 yr. event. There are occasions however,
where the design needs to be based on a "probable maximum
precipitation" (PMP) event . For example, structures that fall within
the control of state regulation. Selecting "P" will cause the program to
user the PMP approach.
Principal Spillway Design Frequency (24 hr) - the default frequency for the
principal spillway routing.
Emergency Spillway Design Frequency (24 hr) - if PMP was selected for the
emergency spillway design, this option will not appear. If is does
appear, enter the value that you want for a default value.
Hydrograph Development Time Increment – this is the time increment that
the program uses to generate the necessary hydrographs. If the
watershed is either extremely small or extremely large, you might
experience anomalies in the results. In these situations it may be
necessary to adjust this time interval. For more details refer to NRCS
technical paper 149.
If you have made changes to this screen, two options will be presented when you exit
from the screen. This first will ask if you want to save the information for future jobs. If
you answer "yes" , the new values will be loaded next time the pond program is run. The
second option asks if you want to use the new values for the current job. A "no" response
will cause the program to revert to the previous values. A "yes" response will cause the
program to use the new values until such time you exit the pond program. The next time
the program is loaded the old values will be used.
Program Details:
This selection will display some of the controlling features of the program as well
as the date of the last change to the program.
Switch Printers:
If you have the ability to use two different printers with your system, this option
will allow you to change the identity of the printer that the program uses. Basically, this
action changes the value of the codes that control the manner in which the printer behaves.
For example, the codes that cause the printer to print in compressed code, etc.
Temporary Exit to DOS:
Many times it would be nice or even necessary to execute a DOS command while
in the program. As an example, you can't remember the subdirectory where your data is so
you need to check several subdirectories or even diskettes. This option will quickly return
to the system prompt and still keep your program and data in memory. When you are ready
to return to the program, simply enter "exit" . There is one important point to
remember! Be certain that you have returned to the subdirectory that contains the
engineering program before entering "exit".
Appendix P
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POND.EXE
Version 2.0
Design
Files
Options
Quit
º
Return to Engineering Menu
Exit to DOS System
Quit:
The response to “quit” can generate several responses depending upon how your
particular system is set up. If the main “engmenu.exe” file is available, you might be
offered an option of returning to the Engineering Menu, exiting to the operating system
(which could be the DOS prompt, windows, or the batch file that originally called the
pond program) or going directly to one of several other engineering programs. If this
“engmenu.exe” file does not exist, you will simply be asked to confirm that you really do
want to quit.
In any case, you will be warned if unsaved data has been entered so that you will have
at least two chances to accidentally lose your data.
Technical Information:
The following information is provided in an effort to make the program more
understandable, creditable and flexible. It might also provide the information necessary to
salvage jobs that have problems and in some situations add data that will improve the
applicability in your locale.
Saved Data Format:
The following is a sample of the form in which data is saved. Spaces have been added
after the delimiters to make it easy to read and the information in the boxes is intended to
identify the data and is not part of the data file.
format key
"Data Format 1.0",
elevation
99.5,
99.7,
99.9,
100.1,
100.3,
100.5,
100.7,
100.9,
101.1,
101.3,
101.5,
0,
0,
0,
job name
"Computer Fair 1993",
area flooded
4.55,
4.65,
4.75,
4.85,
4.95,
5.05,
5.15,
5.25,
5.35,
5.45,
5.55,
0,
0,
0,
county
"Fairfield",
accumulative storage
20.202
21.12198
22.06201
23.02199
24.00201
25.002
26.02198
27.06201
28.12199
29.20202
30.302
0
0
0
Appendix P
Page - 13 -
designer
"cwl",
start elev
88.4
POND.EXE
Version 2.0
0,
0,
0
drainage
area
122,
curve
number
76,
watershed
slope
3,
rainfall
distrib.
"II",
principal
frequency
10,
emergency
frequency
25,
3,
5,
1,
1
99.5,
7.5,
88,
10
5,
2,
3,
12,
18,
1,
"F",
26.9,
25,
.2
0,
0
watershed
length
3770,
time of
concentration
.9972845
principal
design peak
96.52804,
20
principal
type
waterline
elevation
berm
width
freeboard
emergency
design peak
128.7785
principal design
rainfall
3.7
principal material
outlet
elevation
upstream
sideslope
E/S design on
Frequency or
PMP
input hydrograph drainage area
emergency
design rainfall
4.2
emergency
retardance
elev pipe at riser
principal location
top width of dam
downstream pipe
riser
emer
sideslope
diam.
diam. width
Probable
Percent
Increment used
maximum
of PMP
for rating tables
precip.
for design
input hydrograph exists
Note : if an input hydrograph exists, the coordinates will appear here.
Note : if a discharge – rating curve exists, the coordinates will appear here.
<eof>
Pipe Table Format pipes.pnd):
pipe material,
"Smooth iron",
"Concrete",
"Plastic (pvc)",
"Corrugated plastic",
"Corrugated metal",
manning's N
.011
.013
.01
.024
.025
"Standard" File(s) Format:
POND.STD
This file contains the default values that are controlled by the "modify parameters"
option.
"Default Top Width ..........",
"Default Berm Width .........",
"Default Upstream Sideslope .",
"Default Downstream Sideslope",
"Length of Pipe Beyond Dam ..",
"Riser below jct w/ pipe ....",
"Position of Riser ..........",
10
5
2
3
6
1
1
Appendix P
Page - 14 -
POND.EXE
Version 2.0
"Default Principal Spillway Type .....",
3
"Default Principal Spillway Material ",
5
"Default Emergency Spillway Retardance", 1
"Default Principal Spillway Frequency ", 2
"Default Emergency Spillway Frequency ",25
POND.ST2
This is an ASCII file that contains many of the default values and control values used
in pond design. This file is considered "read only" by the program.
"Program Identifier .................................","OH-Ver-1.0"
"Date of last revision to the program ....", "4/14/94"
"Weir flow coefficient ",
3.33
"Use orifice C ## until diam = ## then use orifice C ##", 0.65, 18, .72
This indicates that a orifice control coefficient of 0.65 will be used until the pipe diameter is
eighteen inches and then the coefficient will change to 0.72.
"Pipe Length Variation (ft)",
1
"Minimum Pipe Diameter ",
2
"Maximum Pipe Diameter ",
60
"Maximum Riser Diameter ",
100
"Riser to Pipe Ratio
"
1.25
"Minimum E/S Width
",
4
"Maximum E/S Width
",
200
"Minimum Top Width
",
6
"Maximum Top Width
",
50
"Minimum Berm Width
",
4
"Maximum Berm Width
",
20
"Minimum Sideslope
",
2
"Maximum Sideslope
",
20
"Rainfall Distribution Type",
"II"
"Default Freeboard"
,
1
"Routing Time Increment ", .
1
"Maximum Drainage Area ",
1000
"Storage x Effective Height",
3000
"Effective Height#1 / Storage",
25, 50
"Effective Height#2 / Storage",
35, 15
"Percentage / depth ",
25,
8
"Percentage / depth ",
50,
6
"Top Width / height ", 8, 15, 10, 20, 12, 25, 14, 35, 15, 40
Indicates that an eight foot top width is used to a height of 15 feet, a ten foot top width until twenty
feet in height, etc
"Steepest sideslope / minimum combined ss", 2, 5
"DA / Hght / Freeboard ", 20, 20, 1, 100, 20, 2, 320, 40, 3
"DA / pipe frequency / pipe stage" , 10, 0, .5, 100, 2, ,1 320, 10 ,1
"Pipe Size Options " , 6, 8, 10, 12, 14, 15, 16, 18, 21, 24, 27, 30, 36, 42, 48, 54 ,60
"DA / E/S Freq / Hght / Storage", 20, 10, 20, 50, 20, 25, 20, 50, 20, 25, 20, 50, 50
"State Height / Storage", 6, 15, 10, 50, 25, 50
"Increment used for Discharge-Rating Curve", 0.2
"E/S Design on (F)requency or (P)ercent of PMP","F"
"Percent of PMP used for E/S design", 25
"Override standard 378 stage-freeboard requirements", 0
"Minimum freeboard when complying with 378",1
Appendix P
Page - 15 -
POND.EXE
Version 2.0
Design Details:
The following information is somewhat technical and is included for those individuals
who are skeptical, inquisitive or really care about what is going on.
Basically, three items are necessary in order to flood route a pond structure. They are
a stage - storage relationship, the inflow hydrograph, and a stage - discharge relationship.
Stage - Storage Relationship:
As discussed earlier, the stage - storage relationship is developed within the program.
It begins at the lowest point along the centerline of the embankment. (This value is also
used to classify the structure.) As areas are entered at increments of elevation, the resulting
volumes are calculated. The first increment of storage is calculated using four tenths of the
difference in elevation times the sum of the areas. (The area at the low point is considered
zero.) All subsequent increments of storage are calculated using the average end area
method. The relationship can be developed with as little as two elevations and one area but
the design will be far more accurate if sufficient data is entered to fully define the true
storage capabilities of the site.
Inflow Hydrograph:
If the coordinates of the inflow hydrograph were entered, the program will interpolate
between the coordinates to determine the intermediate values that are needed to do the
routing. If the program is told not to use the input hydrograph or one is not available, it
will generate the inflow hydrographs for the principal and emergency storm events. It used
the data provided, including the deltaD, to build a series of triangular hydrographs and then
adds these hydrographs to form the composite hydrograph. Further details on this
procedure can be found in NRCS Technical Paper 149.
Stage - Discharge Relationship:
If the stage - discharge relationship was entered, the program uses it directly. If there
is not a relationship available, the program builds one using the following equations:
Inlet of hood with H/D < 1.1
Q  ( D / 12)5/ 2  e(ln(H / D)
2
 0.049736 ln( H / D) 1.696568 0.759034)
Slug flow on a hooded inlet.
Q  (( H / D  1.1) / 0. 25  2. 5)  ( D / 12)5/ 2
Appendix P
Page - 16 -
POND.EXE
Version 2.0
Weir flow on the riser:
Q  CAH 3/ 2
Orifice flow at the inlet of the riser and at the inlet of the principal spillway pipe.
Q  CA 2 gH
Full pipe flow:
Q
  D2
4

64. 4  H
2  (5087  n2 / D 4 / 3 )  L
Emergency Spillway flow:
Q  q  ESwidth
Where:
Retardance
Hp
q
B
All values
 4.8585  H p  4.7396
0 to 0.6
 0.6667  H p
C
D
0.6 to 1
 0.065  e
(3.0835H p )
>1
 5  H p  3.5
0 to 0.6
 0.8333  H p
0.6 to 1
 0.0589  e
(3.5835H p )
 5 H p  3
>1
H = head in feet.
D = Diameter of pipe in inches.
C = orifice or weir flow coefficient.
A = cross-sectional area of the pipe.
n = Manning's coefficient
e = 2.71828.
ln = natural logarithm.
q = discharge per foot of width
ESwidth = width of the emergency spillway in feet.
Hp = head on flow in emergency spillway.
Appendix P
Page - 17 -
POND.EXE
Version 2.0
Note:
The equations for the emergency spillway solutions were derived through curve fitting
the data from the NRCS Engineering Field Handbook. It is felt that this solution is
adequate for smaller, shallow flowing, spillways. The results will become increasingly
conservative as the flows become larger. In these cases, more sophisticated methods
should be used to determine the flows with the results incorporated in a discharge rating
curve.
Flood Routing:
I1 
I2
S
Q
S
Q
 1  1  Q1  2  2
2
T
2
T
2
Where:
I = inflow at times 1 and 2.
Q = outflow at times 1 and 2.
S = storage at times 1 and 2.
T = time interval.
Appendix P
Page - 18 -