(HP-67) HNV-SBUH Method (runoff hydrograph-urban basin)

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An extract from Proceedings Stormwater Management Model (SWMM) User's Group Meeting, June 19-20, 1980, USEPA, ERL, R&D, EPA-600/9-80-064, DEC 1980, 244 pages

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Program Descriptions:
          Two separate versions for the HNV-SBUH Method are listed at the end of this paper. The first version requires the manual entrance of each rainfall increment. In the second version, all of the rainfall increments are entered at the start of each program.
Hewlett-Packard (HP) Programs:  The first HP program, referred to as the HP-67 version although it will operate on the HP-97, requires the use of and can be recorded on a single magnetic card. Initially, after the variables are entered and the program started (Press R/S), the infiltration curve is integrated at intervals of 0.01 hours until the volume of water already stored in the soil (=F) is achieved at which time 0.0000000 appears in the display. As previously stated, each rainfall increment must then be manually entered into the calculator, which, when restarted each time (Press R/S), will compute the ordinate of the runoff hydrograph.
          The second HP program, referred to as the HP-97 version, or the HNVSBUH Method-Automatic Version, although it will also operate on the HP-67, has been separated into two different parts each one of which must be recorded on a separate magnetic card.
          In the first part of the program (Card No. 1), the rainfall increments (a maximum of 26) are placed by the program into Storage Registers R11-R19; three each in Storage Registers R11-R18 and two in R19. The maximum rainfall increment that can be placed in any of the registers is 9.99 inches; the minimum is 0.01 inch. The rainfall increments so entered can be recorded on a blank magnetic (data) card for subsequent reuse and thereby avoid the necessity of the individual reentry of same.
          In the second part of the program (Card No. 2) the ordinates of the runoff hydrograph are computed. Initially, as previously stated, the area under the infiltration curve is integrated at time intervals of 0.01 hour until the volume of water already stored in the soil when rainfall begins is achieved (=F). At the conclusion of this operation, the calculator will then automatically start to print the time at the end of each rainfall (=ΣΔt) and the ordinate of the runoff hydrograph Q in cfs at that time. The program stops when the ordinate of the runoff hydrograph <0.01 (0.01 displayed).
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          The volume of runoff in inches (area under the hydrograph) can also be computed by both programs …
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          In both HP versions, the shape (decay) factor Kin Horton's equation may be changed from 2 in the programs by deleting 2 from Steps 10 and 65 of the HP-67 program or from Step 188 of Card No. 2 of the HP-97 program and placing another value at these same locations.
          Detailed User Instructions precede each of the programs listings.
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User instructions & Program Listings - pgs 173-176:

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