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<br />,
<br />I
<br />,
<br />,
<br />
<br />and ground cover, and defines the shape of the runoff hydrograph
<br />for one inch of direct runoff over the area. For storms where
<br />the effective precipitation depth is different from the unit
<br />depth, the actual storm hydrograph is determined by multiplying
<br />the ordinates of the unit hydrograph by the effective precipita-
<br />tion depth and adding to obtain the final storm runoff hydrograph.
<br />
<br />To facilitate accuracy and standardization in developing input
<br />for the effective precipitation, unit hydrograph and storm hydro-
<br />graph operations of the model, a HYDRO data sheet was developed,
<br />as shown in Figure III-I. The input sheet provides tho basin
<br />name and number, which is used primarily for computer identifi-
<br />cation, and also the design point of interest. The section,
<br />township and range of the particular design point was also in-
<br />cluded to assist in the determination of the storm rainfall
<br />depths. Basin parameters were determined from the mapping
<br />available. These parameters included the area, channel length,
<br />channel length closest to the basin centroid and the average
<br />channel slope through the basin. In addition, flow times along
<br />the channel through the basin were computed using a predetermined
<br />design velocity. The degree and type of development within the
<br />basin was noted. When the type of development was quite irregular,
<br />the areas of different development were noted to assist in deter-
<br />mination of various basin characteristics. Basin or hydrological
<br />characteristics included the percentage of pervious and impervious
<br />areas, a constant infiltration rate in inches per hour, pervious
<br />and impervious retention depths, the impervious loss percentage,
<br />and hydrograph time and peak coefficients reflecting the type
<br />~nd degr~e of development. At the bottom of the input sheet
<br />the storm rainfall depths were recorded for the 2, 10 and 100
<br />year frequencies and the 1 and 6 hour durations. These condi-
<br />tions encompassed the range of frequencies and duration of
<br />interest in the study. Additional comments concerning the basin
<br />wpre notpn ~t th~ botto~ of thp Rhppt.
<br />
<br />,
<br />I
<br />,
<br />I
<br />I
<br />
<br />The storm hydrograph coefficients, cp and Ct, which reflect the basin
<br />slope and degree of perviousness or imperviousness, and degree of
<br />sewered area, are b~sed on the valucG recommended in the Urban
<br />Storm Drainaqe Criteria Manual.
<br />
<br />An additional variable in the computation of the unit hydrograph
<br />within the HYDRO model is the unit hydrograph width relationships
<br />at the 50% and 75% peak flow points. For the Sanderson and Weir
<br />studies the most recent width relationship developed by the Urban
<br />Drainaqe and Flood Control District wer.. uS8d which r",rlect
<br />characteristic widths of unit hydrographs in developed urban
<br />areas.
<br />
<br />-22-
<br />
<br />HYDRO DATA SHEET
<br />
<br />DATE: /V~9/7/
<br />BY: .<..-...r
<br />
<br />Basin: NORTk SA/VOERSO/v
<br />
<br />!lasin No.: A/S:5A
<br />
<br />She"t
<br />
<br />J
<br />
<br />of 1
<br />
<br />Location: (ooint of inb'rf',;t)
<br />
<br />,<"LO,ii'/OA AT /3ALSAN CT
<br />
<br />SEe ~C?, 748, ~9.PV
<br />
<br />Rasin Paramc~er5:
<br />
<br />A (sq. mi.) = L"54
<br />
<br />Lea (mL) '" ..-?w"5
<br />
<br />L (mi.)
<br />
<br />= .47~
<br />
<br />Slope (%) = /5
<br />
<br />flow Time
<br />0-10 yrs.
<br />10-100 yrs.
<br />
<br />= E~='~ 60 ""p",."'6~",
<br />"e"OO~<ii.6 .ro.s"'6~"I?
<br />
<br />Degree/~ype of Development,
<br />
<br />Ilydrolo<;i"il.l Cllaracterist:ic'l:
<br />~
<br />~j"ious(%)
<br />Im"crvious (%)
<br />
<br />Stonn ilainta11 II":
<br /> 2 YR.
<br />1 r.r. ,.7
<br />G hr. no
<br />24 C<,
<br />
<br />fA'
<br />
<br />8x1sting ~ ..-'vC~A..L RL;S/DE.NT.4L.., S//VCL2. FA.M/LY,
<br />FZ/LL Y ..o..:V.:L~..Q
<br />
<br />In)
<br />
<br />l:'rOjectedrgJ S4A?".e-
<br />
<br />ICI
<br />
<br />Othor
<br />
<br />r 1
<br />,-
<br />
<br />-
<br />
<br />.~ CT . 5~
<br />55 C, . ~
<br />7~ LD" '" . ~
<br />,50 I:nperv. Ret"ntion
<br />-~-~- (in)
<br /> - ,~
<br />
<br />.
<br />
<br />Infiltration (injllrl =
<br />
<br />"..rv. Retention (in) ..
<br />
<br />10 YR.
<br />
<br />100 YR.
<br />
<br />S:i'P
<br />
<br />,'.~r
<br />
<br />f~5
<br />
<br />z/o
<br />
<br />-"""'"
<br />
<br />S~
<br />
<br />Comments:
<br />~.....!.. S.!..oPEO., S""",,J23E.!..Y' .,SEvv,€QE-D
<br />
<br />Fi.,;Llh.111-1
<br />
<br />-23-
<br />
<br />FRASIER S GI~G~RY, I~C.
<br />Cons'..lting ~'ngin"crs
<br />
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