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Pervious Retention - Rainfall that is retained in small depressions and on vegetation and does not contribute to the runoff from the basin, expressed as an equivalent depth of rainfall. TABLE 111-' DRAINAGE BASIN CHARACTERISTICS WOMAN CREEK, WAlNUT CREEK, UPPER BIG DRY CREEK: AND ACX;K CREEK . Impervious Retention - Rainfall that is retained in depressions on roofs, paved parking lots and paved roads and does not contribute to runoff from the basin, expressed as an equivalent depth of rainfall. PLAN BASIN BASIN BASIN BASIN IMPERVIOUS IMPEFMOUS PElM>US IMPERVIOUS INFilTRATION SWMM DESIGNATION AREA LENGTH Lea SLOPE EXISTING DEVELOPED RETENT10N ReTENTlON I INITlAL. FINAL DECAY Te BASIN (SQMq (Mq (Mq (FTIFT) I'l'I I'l'I QN) QN) QNlHR) QNlHR) (MIN) NUMBER WAlNUT CREEK BASIN. PLANT SITE BUFFER AREA WAl 0.377 0.507 0.284 0.015 1 . 0." 0.10 '""0 0.51 0.0017 28 WA2 0.089 0.374 0.213 0.021 0 . 0." 0.10 1.110 0.51 0.0017 34.0 28 A3 0.213 0.578 0.'" 0.028 0 . 0.47 0.10 2.15 0.52 0.0018 38 WAA O.2S2 1.184 0.851 0.034 0 . 0.51 0.10 3.110 0." 0.0012 30 WA5 0.154 0.... 0._ 0.037 0 . 0.44 0.10 2.00 0.52 O.(Xlle 31 WAll 0.319 1.402 0.748 0.039 0 . 0." 0.10 1.50 0.51 0.0017 38 WA7 0.0110 0.'" 0.213 0.037 8 8 0.50 0.10 3.50 0." 0.0013 32.' <0 WAll 0.044 0.803 0.'" 0.017 0 . 0.110 0.10 8.00 0.110 0.0007 83.1 41 WAll O.OBO 0.833 0.374 0.041 0 . 0." 0.10 1.75 0.52 0.0016 52.7 27 WA10 0.208 I.OBB 0.'" 0.034 2 . 0." 0.10 2.00 0.52 0.0018 28 All 0.192 0.... 0.450 0.028 . . 0." 0.10 1.30 0.50 0.0018 .. WA12 0.063 0.294 0.188 0.038 0 . 0." 0.10 1.70 0.50 0.0018 24.7 .. WA13 0.073 0.625 0.313 0.032 28 30 0.52 0.10 4.00 0." 0.0011 .... .. WA14 0.0<0 0.348 0.161 0.028 . . 0.52 0.10 4.00 0." 0.0011 28.0 .. WA15 0.232 1.241 0.758 0.015 0 . 0.110 0.10 8.00 0.110 0.0007 32 SWA1 0.047 0.237 0.142 0.057 7 12 0.<0 0.10 1.00 0.50 0.0018 10.0 .. SWA2 0.038 0..... 0.313 0.018 4 . 0.110 0.10 8.00 0.110 0.0007 61.3 .. SWA3 0.""" 0.... 0.242 0.020 3 . 0." 0.10 2.00 0.52 0.0016 33.0 " WADlV1 0.078 0.720 0.308 0.018 0 . 0.110 0.10 8.00 0.110 0.0007 83.0 34 WADIV2 0.... 1.207 0.521 0.024 1 . 0.110 0.10 8.00 0.110 0.0007 30 WADIV3 0.011 0.00. 0.047 0.024 1 . 0.110 0.10 8.00 0.110 0.0007 32.0 36 ADIV4 0.017 0.... 0.478 0.018 0 . 0.110 0.10 8.00 0.110 0.0007 38.3 33 WALNUT CREEK BASIN. PLANT SITE CORE AREA CWADlVA 1 0.031 0.... 0.142 0.013 00 OB 0.<0 0.10 8.00 0.110 0.0007 18.5 .. W 0.""" 0.341 0.170 0.015 110 OB 0.<0 0.10 8.00 0.110 0.0007 22.4 .. CSWAA 0.1n 1.212 O.BOB 0.014 B3 OB 0.<0 0.10 8.00 0.110 0.0007 .. CSWAB 0.189 1.023 0.511 0.024 70 OB 0.<0 0.10 4.20 0." 0.0011 50 CWAA, 0.023 0.057 0.037 0.""" 50 OB 0.<0 0.10 2.110 0.33 0.0015 '''4 52 CW 0.017 0.198 O.OBO 0.032 50 OB 0.<0 0.10 8.00 0.110 0.0007 18.4 " CWAC 0.183 0.000 0.455 0.031 .. OB 0.<0 0.10 4.30 0.57 0.0011 33 WALNUT CREEK ElASIN . OUTSIDE OF PlANT SITE 1 0.801 0.800 0.237 0.""" 0 . 0." 0.10 1.30 0.50 0.0018 - 28 0.249 100 100 0.00 0.00 0.00 0.00 0.0000 2. WAL1 0.240 1.667 0.753 0.028 0 . 0.110 0.10 8.00 0.110 0.0007 37 WOMAN K BASIN - PlANT S U EA Wl 0.447 1.515 0.724 0.020 0 . 0." 0.10 1.<0 0.50 0.0018 8 W2 0.089 0.450 0.223 0.023 0 . 0." 0.10 1.<0 0.50 0.0018 38.3 0 W3 0.182 0.450 0.213 0.021 2 . 0." 0.10 1.30 0.50 0.0018 10 4 0.241 1.373 0.0<0 0.032 0 . 0.50 0.10 3.50 0." 0.0013 11 W' 0.214 0.814 0.818 0.028 0 . 0." 0.10 2.10 0.51 0.0017 12 WB 0.282 1.278 0.891 0.031 1 . 0." 0.10 3.110 0.... 0.0014 13 W7 0.361 1.278 0.887 0.038 0 . 0." 0.10 4.75 0." 0.0010 .. WO 0.'" 1.383 0.474 0.033 2 . 0.<0 0.10 1.00 0.50 0.0018 1. WB 0.12S 0.... 0.288 0.0<0 1 . 0.<0 0.10 1.00 0.50 0.0018 36.7 18 SWl 0.270 I.OBB 0.729 0.020 0 . 0.50 0.10 2.00 0.50 0.0018 17 W2 1.178 2.300 1.278 0.030 0 . 0.52 0.10 3.70 0." 0.0013 10 SW3 0.097 0.379 0.189 0.020 .. .. 0.<0 0.00 8.00 0.110 0.0007 23.4 10 OlYl 0.030 0.175 0.000 0.033 .. 10 0." 0.10 1.110 0.50 0.0018 21.9 20 IY2 0.119 0.... 0.213 0.028 2 . 0." 0.10 2.50 0.33 0.0015 37.8 21 DIV3 0.152 1.184 0.'" 0.032 .. 10 0." 0.10 2.00 0.52 0.0018 22 WOMAN CREEK BASIN. OUTSIDE OF PLANT SfTE SLA 1.000 '00 100 0.00 0.00 0.00 0.00 0.0000 1 11 2.3110 2.188 0.IlOO 0.019 . . 0.<0 O.fO 1.30 0.50 0.OOf8 2 WOMl O.BOO 1.878 0.521 0.030 0 . 0.110 0.10 8.00 0.110 0.0007 23 U ERBIG AY A I Sl2 1.470 1.373 0.000 0.017 1 . 0." 0.10 1.50 0.50 0.0018 3 S1.3 0.850 0.758 0.... 0.03. 7 '2 0.<0 0.10 1.00 0.50 0.0018 4 Sl4 2.710 3.712 1.136 0.030 1 . 0." 0.10 1.00 0.52 0.0018 . 0.810 1.320 0.330 0._ 4 . 0.<0 0.10 1.00 0.50 0.0018 - 110 Sl.O 0.000 2.230 1.0lIO 0.029 0 . 0.110 0.10 8.00 0.110 0.0007 0 SLB 1.370 1.941 0.... 0.033 . . 0." 0.10 1.20 O.!lO 0.0018 - 7 KC IN ACl 2.080 2.... 1.... 0.031 10 1. 0.33 0.10 3.110 0." 0.0013 .. AC2 0.3llO 1.()" 0.347 0.028 0 . 0.110 0.10 8.00 0.110 0.0007 .71 Infiltration - The potential passage of water through the soil surface into the soil. The maximum infiltration rate exists at the beginning of rainfall and is termed the "initial infiltration rate." As the soil profile tends to become saturated, the infiltration capacity decreases and approaches a constant rate termed the "final infiltration rate." The exponential decay rate from the initial infiltration capacity to the final infiltration capacity is used to determine the infiltration losses. These three infiltration values are used in Horton's equation to yield an infiltration rate at any period during a runoff event. . Tc - Time of concentration is the time it takes for a drop of rainfall to travel from the upstream end of the basin to the basin outlet. . Basin Number - Identifies the basin in the Stormwater Management Model (SWMM). . Basin Designation - Identifies the basin in the Colorado Urban Hydrograph Procedure model (CUHP). The characteristics of each drainage basin are presented in Table ill-I. DRAINAGE BASIN DESCRIPTIONS The hydrological parameters for each of the major drainage basins west of Indiana Street are summarized below. The total area of the Walnut Creek, Woman Creek and Upper Big Dry Creek drainage basins between the headwaters and Indiana Street is approximately 12.9 square miles. The hydrological parameters have been reviewed by UDFCD and the State of Colorado and were found to be reasonable and appropriate (see Appendix II-A to the introduction to this Master Plan).