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<br />In calculating time response T6" a problem was
<br />
<br />encountered using program FINVER. The location of the
<br />unit hydrograph in time is lost and the relative loca-
<br />tion of the peak is not possible. In calculating Tc
<br />
<br />(T8) , several rainfall events were found which did not
<br />
<br />end in a clear and definite manner, but rather con-
<br />tinued contributing very small amounts of rainfall past
<br />the point of inflection of the runoff hydro graph at a
<br />relatively constant rate. The end of rainfall in these
<br />cases was interpreted to be at the end of the last
<br />volume observed before the rainfall rate became con-
<br />stant.
<br />
<br />The centroids of the excess rainfall and the run-
<br />off were obtained by tracing the graphs with a digiti-
<br />zer which punched the coordinates on cards. A computer
<br />program was then used to calculate the coordinates of
<br />the centroids.
<br />
<br />RAINFALL PARAMETERS
<br />
<br />The rainfall producing the runoff influences the
<br />hydro graph in a number of ways. The concept of the
<br />unit hydro graph and unit duration of rainfall excess
<br />tend to remove some of these variations. The rainfall
<br />parameters used in this investigation are given in
<br />Table 7.
<br />
<br />Table 7
<br />
<br />Rainfall Parameters
<br />Lopez (1973)
<br />
<br />Definition
<br />
<br />Units
<br />
<br />VRF
<br />
<br />Total volume of rainfall during storm
<br />considered average over the watershed.
<br />(Size of storm) inches
<br />
<br />ERF
<br />
<br />Volume of rainfall excess.
<br />sidered equal to the volume
<br />runoff.
<br />
<br />inches
<br />
<br />Is con-
<br />of direct
<br />
<br />RFLOSS
<br />
<br />That part of
<br />not appearing
<br />
<br />Volume of rainfall loss.
<br />the total storm rainfall
<br />as runoff.
<br />
<br />Duration of total storm rainfall
<br />
<br />inches
<br />minutes
<br />
<br />T10
<br />
<br />PHYSICAL WATERSHEO PARAMETERS
<br />
<br />Since the work of Mulvaney in 1851.
<br />nized that urbanization produces changes
<br />cal character of drainage basin. Some of
<br />in the watershed change the watershed
<br />characteristics. the watershed response
<br />watershed storage characteristics.
<br />
<br />it was recog-
<br />in the physi-
<br />these changes
<br />infiltration
<br />time, and the
<br />
<br />The effect of urbanization on the changes in the
<br />hydrologic characteristics are sometimes influenced by
<br />local building codes. construction procedures or by
<br />requirements established for Federal assistance from
<br />VA. FHA and HUD. Various physical variables which
<br />other research has shown to be important hydrologic
<br />variable~ have .been measured. Some of these variables
<br />have been combined into parameters and the effect of
<br />
<br />these variables or parameters was related to the run-
<br />off hydrograph by means of a stepwise multiple regres-
<br />sion. The values of these rainfall parameters given in
<br />Table 8.
<br />
<br />Rainfall-Runoff Paramet~rs for Denver Watersheds
<br />
<br />Table 8
<br />
<br />Catchllent
<br />
<br />Big Dry Cr. Trib.
<br />at Littleton. CO
<br />
<br />Sanderson Gulch
<br />Trib.at
<br />Lakewood, co
<br />
<br />SchnelderDrain
<br />at Arvada.. co
<br />Toll Gate Cr. Trib.
<br />at Aurora., CO
<br />
<br />Westerly Cr. Trib.
<br />at Aurora, CO
<br />Concourse 0
<br />StOI'lll Drain at
<br />Stapleton Airport
<br />Tuck Drain at
<br />Northglenn, CO
<br />
<br />Hillcre~t Drain at
<br />Northglenn.CO
<br />
<br />Kennedy Drive Drain
<br />at Northglenn, CO
<br />
<br />The
<br />abIes of
<br />them are
<br />
<br />CSU Qp/A '" E" RFLOSS T"
<br />"", (in./hr.) (in.) (in.) (in.) (min.)
<br />1060702001 1.580 ,17 .055 .135 2S
<br />1060702002 1.069 ,26 .025 .235 55
<br />1060702003 1.588 ,,, .072 .148 15
<br />1060702004 1.596 ,35 .072 .278 "
<br />1060702005 .641 ,75 .245 .505 35
<br />1060716001 3.400 ,,, .025 .195 15
<br />1060716002 4.000 ,26 .012 .248 20
<br />1060716005 3.307 ,49 .060 .430 15
<br />1060716004 2.194 ,41 .110 .300 2S
<br />106071fJ005 1.357 ," .116 .204 70
<br />1060798001 4.310 ,OS .023 .027 I'
<br />1060798002 3.431 ," .048 .292 15
<br />1060142302 2.755 ,71 .240 .470 70
<br />1060742305 2.949 1.09 .245 .845 "
<br />1060742307 2.360 ,5S .260 .390 100
<br />1060742306 2.484 ,49 .145 .295 35
<br />1060741708 1.294 ,04 .BO .310 35
<br />1060745002 3.240 ," .148 .222 20
<br />1060701001 4.272 ,I' .068 .072 15
<br />1060701002 3.143 ,26 .252 .128 40
<br />1060701003 5.653 ," .L76 ,OM 35
<br />1060701008 5.800 ,,, .108 .162 2S
<br />1060701011 3.099 ," .224 .076 2S
<br />1060703001 S.246 ,58 .040 .540 40
<br />IOfJ0703002 4.660 ,,, .010 .210 35
<br />1060703005 3.188 ,'I .028 .282 49
<br />1060703009 .l.S86 ,I' .031 .410 "
<br />IOfJ0103010 3.514 ,'" .055 .245 30
<br />1060103015 ,I' .108 .082 50
<br />1060703016 4.660 ," .O2!> .ZlS 20
<br />1060704001 6.652 ,'I .108 .302 10
<br />1060704002 !>.423 ,,, .074 .156 40
<br />106()704003 6.632 .38 .145 .n5 2S
<br />1060104004 6.632 ," .128 .H2 20
<br />
<br />watershed vari-
<br />used in obtaining
<br />
<br />definitions of the physical
<br />the basin and the methods
<br />given as follows:
<br />
<br />a) Length of Paved Streets
<br />
<br />length of all paved streets and
<br />obtained from aerial photographs
<br />the city engineer's offices.
<br />
<br />and Roads, LpSR--The
<br />roads, in miles. was
<br />and records kept by
<br />
<br />b) Length of Curbed and Guttered Streets, LeG--
<br />
<br />The length of paved, curbed and guttered streets, in
<br />miles, was obtained as in (a) above.
<br />
<br />c)
<br />length
<br />curbed
<br />
<br />Length of Unpaved Streets and Roads, LUSRuThe
<br />
<br />of unpaved streets and roads, in miles, whether
<br />and guttered or not was obtained as in (a).
<br />
<br />d) Length of Streets and Roads. LSR--The sum
<br />
<br />total of all lengths of streets and roads. in miles,
<br />whether paved, unpaved. with and without curb and
<br />gutter.
<br />
<br />e) Length of Storm Sewer. Lss--The length of
<br />
<br />storm sewers in miles, was obtained from Has built"
<br />drawings generally kept at the jurisdictional city
<br />
<br />18
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