|
<br />Hypothetical River near Example
<br />
<br />I
<br />
<br />Time, hours
<br />18.75
<br />22.50
<br />26.25
<br />30.00
<br />33,75
<br />37.50
<br />41.25
<br />45.00
<br />48.75
<br />52.50
<br />56.25
<br />60.00
<br />63,75
<br />67.50
<br />71.25
<br />75.00
<br />
<br />Discharge
<br />3574,
<br />4765,
<br />6254,
<br />7743.
<br />9827.
<br />11912,
<br />14592,
<br />17272,
<br />19952,
<br />22633.
<br />25015.
<br />26802,
<br />28291.
<br />29184.
<br />29780,
<br />29482,
<br />
<br />180,00 3276,
<br />183.75 2978,
<br />A lagtime (LT) of 75 hours was used in the above example.
<br />
<br />i
<br />,
<br />I
<br />!
<br />!
<br />
<br />The flood-hydro graph ordinates can also be output in a for-
<br />mat that is used in the Federal Highway Administration
<br />HYDRAIN series of programs (HYDRAIN Version 5.0:
<br />Integrated Drainage Design Computer System, Publication
<br />No, FHWA-RD,92,06I, July 1994), The format of the
<br />HYDRAIN output file is as follows:
<br />
<br />Description
<br />Line I:
<br />Line 2:
<br />Line 3+(N-l):
<br />
<br />Flood--hydrograph ordinates:
<br />Fonnat
<br />
<br />Comment line
<br />Number of points
<br />N. T(N), Q(N)
<br />
<br />A73
<br />110
<br />FIO,O, FIO,I. FIO.3
<br />
<br />where N = point number
<br />T(N) = time, in minutes for point N
<br />Q(N) = flow value. in cubic feet per second, for point
<br />N
<br />
<br />An example of the HYDRAIN format follows:
<br />0912111994 10:33 Hypothetical River near Example (HYD-
<br />RAIN Format)
<br />45
<br />
<br />o
<br />I
<br />2
<br />3
<br />4
<br />5
<br />6
<br />
<br />1125,
<br />1350.
<br />1575.
<br />1800,
<br />2025,
<br />2250,
<br />2475.
<br />
<br />3574,
<br />4765,
<br />6254.
<br />7743,
<br />9827,
<br />11912,
<br />14592,
<br />
<br />7
<br />8
<br />9
<br />10
<br />II
<br />12
<br />13
<br />14
<br />15
<br />
<br />2700.
<br />2925,
<br />3150,
<br />3375.
<br />3600.
<br />3825,
<br />4050.
<br />4275,
<br />4500,
<br />
<br />17272.
<br />19952.
<br />22633.
<br />25015.
<br />26802,
<br />28291.
<br />29184,
<br />29780.
<br />29482,
<br />
<br />43
<br />44
<br />
<br />10799.
<br />11024,
<br />
<br />3276.
<br />2978,
<br />
<br />The constants and coefficients for the regression equations
<br />are stored in the state-by-state data base in NFF. The general
<br />form of the equations used to calculate the flood-peak dis-
<br />charges for each recurrence interval is as follows: (For a few
<br />States. a different form of equation was used and these are
<br />documented in the individual State sections.)
<br />RQx=C'Flel'F/2... .
<br />where RQx = rural flood-peak discharge for recurrence inter-
<br />val x
<br />C = regression constant,
<br />Fj = watershed and climatic characteristic i (Note -
<br />The Fi values may be transformed by a modifier
<br />by the addition, subtraction, or division of a
<br />constant),
<br />ei = regression coefficients or exponents for water-
<br />shed or climatic characteristic i.
<br />
<br />The following information is stored in the state-by-state data
<br />files. However, to insure the integrity of the computer pro-
<br />gram, the following information is stored in a binary com-
<br />pressed file in the program and cannot be changed or viewed
<br />by the user, The purpose of providing the following informa-
<br />tion is to illustrate the information used in the computer pro-
<br />gram and to document the format of this information.
<br />The following information is stored for each State:
<br />
<br />Title Comment
<br />
<br />State Abbreviation Abbreviation of state.
<br />Examples: AL
<br />SC
<br />
<br />State Name Name of state,
<br />Examples: Alabama
<br />South,Carolina
<br /># of hydrologic regions Integer number of hydrologic regions
<br />within state.
<br />
<br />APPENDIX B - DESCRIPTION OF THE NATIONAL FLOOD FREQUENCY PROGRAM 191
<br />
|