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HomeMy WebLinkAboutDetention Calculations Detention Calculations - Modified Rational Method 1 00 Year Storm Exst Drainage Area (acr 0.51 Existing C Factor 0.25 Existing Tc (min) 5 Fut Drainage Area (acre 0.51 Future C Factor 0.93 Future Tc min 0.5 Computed Allowable Discharge: Allowable Discharge per Greg Hoys: 1.45 cfs 0.12 cfs 0.22 acre ft @ Duration of: 360 minutes Rainfall Data I Tc 1100 ID Duration Q in Qout Inflow Outflow Storage Storage (min) (in/hr) (min) (cfs) (cfs) (cu ft) (cu ft) (cu ft) (ac ft) 5 9.12 5 5.4 0.1 1 ,622 20 1,602 0.0368 10 7.78 10 4.6 0.1 2,768 38 2,730 0.0627 15 6.77 15 4.0 0.1 3,612 56 3,557 0.0816 20 5.99 20 3.6 0.1 4,262 74 4,188 0.0961 30 4.84 30 2.9 0.1 5, 165 110 5,055 0.1161 40 4.05 40 2.4 0.1 5,763 146 5,617 0.1289 50 3.47 50 2.1 0.1 6,172 182 5,990 0.1375 60 3.03 60 1.8 0.1 6,467 218 6,249 0.1435 90 2.24 90 1.3 0.1 7,171 326 6,846 0.1572 120 1.87 120 1.1 0.1 7,982 434 7,549 0.1733 180 1.42 180 0.8 0.1 9,092 650 8,443 0.1938 240 1.15 240 0.7 0.1 9,818 866 8,952 0.2055 300 0.97 300 0.6 0.1 9,270 0.2128 420 0.75 420 0.4 0.1 11 ,205 1,514 9,692 0.2225 480 0.67 480 0.4 0.1 11,440 1 ,730 9,710 0.2229 540 0.61 540 0.4 0.1 11,718 1 ,946 9,772 0.2243 600 0.56 600 0.3 0.1 11,952 2,162 9,791 0.2248 720 0.48 720 0.3 0.1 12,294 2,594 9,700 0.2227 840 0.42 840 0.2 0.1 12,550 3,026 9,524 0.2186 960 0.38 960 0.2 0.1 12,977 3,458 9,519 0.2185 1080 0.34 1080 0.2 0.1 13,062 3,890 9,172 0.2106 1200 0.31 1200 0.2 0.1 13,233 4,322 8,911 0.2046 1440 0.27 1440 0.2 0.1 13,831 5, 186 8,645 0.1985 1 of 7 Detention Calculations - Modified Rational Method 50 Year Storm Exst Drainage Area (acr 0.51 Existing C Factor 0.25 Existing Tc (min) 5 Fut Drainage Area (acre 0.51 Future C Factor 0.93 Future T c min 0.5 Computed Allowable Discharge: Allowable Discharge per Greg Hoys: 1.29 cfs 0.12 cfs 0.19 acre ft @ Duration of: 240 minutes Rainfall Data I Tc 150 ID Duration Q in Qout Inflow Outflow Storage Storage (min) (in/hr) (min) (cfs) ( cfs ) (cu ft) (cu ft) (cu ft) (ac ft) 5 8.09 5 4.8 0.1 1,439 20 1,419 0.0326 10 6.90 10 4.1 0.1 2,455 38 2,417 0.0555 15 6.01 15 3.6 0.1 3,207 56 3,151 0.0723 20 5.31 20 3.1 0.1 3,778 74 3,704 0.0850 30 4.29 30 2.5 0.1 4,578 110 4,468 0.1026 40 3.59 40 2.1 0.1 5,108 146 4,962 0.1139 50 3.07 50 1.8 0.1 5,460 182 5,279 0.1212 60 2.68 60 1.6 0.1 5,720 218 5,502 0.1263 90 1.91 90 1.1 0.1 6, 115 326 5,789 0.1329 120 1.60 120 0.9 0.1 6,830 434 6,396 0.1468 180 1.22 180 0.7 0.1 7,812 650 7, 162 0.1644 300 0.83 300 0.5 I 0.1 8,858 1 ,082 7,776 0.1785 360 0.72 360 0.4 0.1 9,220 1 ,298 7,923 0.1819 420 0.64 420 0.4 0.1 9,562 1 ,514 8,048 0.1848 480 0.57 480 0.3 0.1 9,733 1 ,730 8,003 0.1837 540 0.52 540 0.3 0.1 9,989 1 ,946 8,043 0.1846 600 0.48 600 0.3 0.1 10,245 2, 162 8,083 0.1856 720 0.41 720 0.2 0.1 1 0,501 2,594 7,907 0.1815 840 0.36 840 0.2 0.1 10,757 3,026 7,731 0.1775 960 0.32 960 0.2 0.1 10,928 3,458 7,470 0.1715 1080 0.29 1080 0.2 0.1 11,141 3,890 7,252 0.1665 1200 0.27 1200 0.2 0.1 11,525 4,322 7,204 0.1654 1440 0.23 1440 0.1 0.1 11 ,782 5, 186 6,596 0.1514 20f7 Detention Calculations - Modified Rational Method 25 Year Storm Exst Drainage Area (acr 0.51 Existing C Factor 0.25 Existing Tc (min) 5 Fut Drainage Area (acre 0.51 Future C Factor 0.93 Future Tc min 0.5 Computed Allowable Discharge: Allowable Discharge per Greg Hoys: 1.14 cfs 0.12 cfs 0.15 acre ft @ Duration of: 240 minutes Rainfall Data I Tc 125 10 Duration Q in Qout Inflow Outflow Storage Storage (min) (in/hr) (min> ( cfs ) ( cfs ) (cu ft) (cu ft) (cu ft) lac ft) 5 7.17 5 4.3 0.1 1,275 20 1 ,255 0.0288 10 6.12 10 3.6 0.1 2, 177 38 2,139 0.0491 15 5.33 15 3.2 0.1 2,844 56 2,788 0.0640 20 4.71 20 2.8 0.1 3,351 74 3,277 0.0752 30 3.81 30 2.3 0.1 4,066 110 3,956 0.0908 40 3.18 40 1.9 0.1 4,525 146 4,379 0.1005 50 2.73 50 1.6 0.1 4,856 182 4,674 0.1073 60 2.38 60 1.4 0.1 5,080 218 4,862 0.1116 90 1.63 90 1.0 0.1 5,218 326 4,893 0.1123 120 1.37 120 0.8 0.1 5,848 434 5,414 0.1243 180 1.04 180 0.6 0.1 6,659 650 0.1380 300 0.71 300 0.4 0.1 7,577 1 ,082 6,495 0.1491 360 0.62 360 0.4 0.1 7,940 1 ,298 6,642 0.1525 420 0.55 420 0.3 0.1 8,217 1,514 6,703 0.1539 480 0.49 480 0.3 0.1 8,367 1 ,730 6,637 0.1524 540 0.45 540 0.3 0.1 8,644 1 ,946 6,698 0.1538 600 0.41 600 0.2 0.1 8,751 2,162 6,589 0.1513 720 0.35 720 0.2 0.1 8,964 2,594 6,370 O. 1462 840 0.31 840 0.2 0.1 9,263 3,026 6,237 0.1432 960 0.28 960 0.2 0.1 9,562 3,458 6,104 0.1401 1080 0.25 1080 0.1 0.1 9,605 3,890 5,715 0.1312 1200 0.23 1200 0.1 0.1 9,818 4,322 5,496 0.1262 1440 0.20 1440 0.1 0.1 10,245 5, 186 5,059 0.1161 30f7 Detention Calculations - Modified Rational Method 1 0 Year Storm Exst Drainage Area (acr 0.51 Existing C Factor 0.25 Existing Tc (min> 5 Fut Drainage Area (acre 0.51 Future C Factor 0.93 Future Tc min 0.5 Computed Allowable Discharge: Allowable Discharge per Greg Hoys: 0.98 cfs 0.12 cfs 0.12 acre ft @ Duration of: 180 minutes Rainfall Data I Tc 110 10 Duration Q in Qout Inflow Outflow Storage Storage (min) (in/hr) (min) l cfs ) ( cfs ) (cu ft) (cu ft) (cu ft) (ac ft) 5 6.12 5 3.6 0.1 1 ,089 20 1 ,069 0.0245 10 5.22 10 3.1 0.1 1,857 38 1,819 0.0418 15 4.55 15 2.7 0.1 2,428 56 2,372 0.0545 20 4.02 20 2.4 0.1 2,860 74 2,786 0.0640 30 3.25 30 1.9 0.1 3,468 110 3,359 0.0771 40 2.71 40 1.6 0.1 3,856 146 3,710 0.0852 50 2.33 50 1.4 0.1 4,144 182 3,962 0.0910 60 2.03 60 1.2 0.1 4,333 218 4,115 0.0945 90 1.42 90 0.8 0.1 4,546 326 4,220 0.0969 120 1.11 120 0.7 0.1 r, 434 4,304 0.0988 240 0.68 240 0.4 0.1 5,805 866 4,940 O. 1134 300 0.58 300 0.3 0.1 6, 190 1 ,082 5,108 0.1173 360 0.50 360 0.3 0.1 6,403 1 ,298 5,105 0.1172 420 0.44 420 0.3 0.1 6,574 1,514 5,060 O. 1162 480 0.40 480 0.2 0.1 6,830 1 ,730 5,100 0.1171 540 0.36 540 0.2 0.1 6,915 1 ,946 4,969 0.1141 600 0.33 600 0.2 0.1 7,043 2,162 4,882 0.1121 720 0.29 720 0.2 0.1 7,428 2,594 4,834 0.1110 840 0.25 840 0.1 0.1 7,470 3,026 4,444 0.1020 960 0.23 960 0.1 0.1 7,854 3,458 4,397 0.1009 1080 0.20 1080 0.1 0.1 7,684 3,890 3,794 0.0871 1200 0.19 1200 0.1 0.1 8,111 4,322 3,789 0.0870 1440 0.16 1440 0.1 0.1 8,196 5,186 3,010 0.0691 40f7 Detention Calculations - Modified Rational Method 5 Year Storm Exst Drainage Area (acr 0.51 Existing C Factor 0.25 Existing Tc (min> 5 Fut Drainage Area (acre 0.51 Future C Factor 0.93 Future Tc min 0.5 Computed Allowable Discharge: Allowable Discharge per Greg Hoys: 0.87 cfs 0.12 cfs 0.10 acreft @ Duration of: 60 minutes Rainfall Data I Tc 15 10 Duration Q in Qout Inflow Outflow I Storage Storage (min) (in/hr) (min) ( cfs ) ( cfs ) (cuft) (cu ft) (cu ft) (ac ft) 5 5.43 5 3.2 0.1 966 20 946 0.0217 10 4.63 10 2.7 0.1 1,647 38 1 ,609 0.0369 15 4.03 15 2.4 0.1 2,150 56 2,095 0.0481 20 3.56 20 2.1 0.1 2,533 74 2,459 0.0565 30 2.88 30 1.7 0.1 3,073 110 2,964 0.0680 40 2.41 40 1.4 0.1 3,429 146 3,283 0.0754 50 2.06 50 1.2 0.1 182 3,482 0.0799 90 1.23 90 0.7 0.1 3,938 326 3,612 0.0829 120 0.95 120 0.6 0.1 4,055 434 3,621 0.0831 180 0.72 180 0.4 0.1 4,610 650 3,960 0.0909 240 0.58 240 0.3 0.1 4,952 866 4,086 0.0938 300 0.49 300 0.3 0.1 5,229 1,082 4,147 0.0952 360 0.43 360 0.3 0.1 5,507 1 ,298 4,209 0.0966 420 0.38 420 0.2 0.1 5,677 1,514 4,164 0.0956 480 0.34 480 0.2 0.1 5,805 1 ,730 4,076 0.0936 540 0.31 540 0.2 0.1 5,955 1 ,946 4,009 0.0920 600 0.28 600 0.2 0.1 5,976 2, 162 3,814 0.0876 720 0.24 720 0.1 0.1 6,147 2,594 3,553 0.0816 840 0.22 840 0.1 0.1 6,574 3,026 3,548 0.0815 960 0.19 960 0.1 0.1 6,488 3,458 3,031 0.0696 1080 0.17 1080 0.1 0.1 6,531 3,890 2,641 0.0606 1200 0.16 1200 0.1 0.1 6,830 4,322 2,508 0.0576 1440 0.14 1440 0.1 0.1 7,171 5, 186 1 ,986 0.0456 50f7 , , .. . Detention Calculations - Modified Rational Method 2 Year Storm Exst Drainage Area (acr 0.51 Existing C Factor 0.25 Existing Tc (min> 5 Fut Drainage Area (acre 0.51 Future C Factor 0.93 Future T c min 0.5 Computed Allowable Discharge: Allowable Discharge per Greg Hoys: 0.74 cfs 0.12 cfs 0.07 acre ft @ Duration of: 60 minutes Rainfall Data I Tc 12 10 Duration Q in Qout Inflow Outflow Storage Storage (min) (in/hr) (min) ( cfs ) l cfs ) (cu ft) l cu ft) (cu ft) (ac ft) 5 4.63 5 2.7 0.1 824 20 804 0.0185 10 3.95 10 2.3 0.1 1 ,405 38 1,367 0.0314 15 3.44 15 2.0 0.1 1 ,836 56 1 ,780 0.0409 20 3.04 20 1.8 0.1 2,163 74 2,089 0.0480 30 2.46 30 1.5 0.1 2,625 110 2,515 0.0577 40 2.05 40 1.2 0.1 2,917 146 2,771 0.0636 50 1.76 50 1.0 0.1 3, 130 182 2,949 0.0677 90 1.07 90 0.6 0.1 3,426 326 3,100 0.0712 120 0.83 120 0.5 0.1 3,543 434 3,109 0.0714 180 0.59 180 0.3 0.1 3,778 650 3,128 0.0718 240 0.47 240 0.3 0.1 4,013 866 3,147 0.0722 300 0.40 300 0.2 0.1 4,269 1 ,082 3,187 0.0732 360 0.35 360 0.2 0.1 4,482 1 ,298 3,184 0.0731 420 0.31 420 0.2 0.1 4,632 1 ,514 3,118 0.0716 480 0.28 480 0.2 0.1 4,781 1 ,730 3,051 0.0700 540 0.25 540 0.1 0.1 4,802 1 ,946 2,856 0.0656 600 0.23 600 0.1 0.1 4,909 2,162 2,747 0.0631 720 0.20 720 0.1 0.1 5,122 2,594 2,529 0.0580 840 0.17 840 0.1 0.1 5,080 3,026 2,054 0.0472 960 0.16 960 0.1 0.1 5,464 3,458 2,006 0.0461 1080 0.14 1080 0.1 0.1 5,379 3,890 1 ,489 0.0342 1200 0.13 1200 0.1 0.1 5,549 4,322 1 ,228 0.0282 1440 0.11 1440 0.1 0.1 5,635 5, 186 449 0.0103 60f7