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" 2-HOUR, AND 6-HOUR STORMS 1-HOUR, RAINFALL DISTRIBUTION FOR ~ OO-year storm 6-HR STORM EVENT DISTRIBUTION for 6-Hour Storm Depths based on USGS storm distribution 2-HR STORM EVENT DISTRIBUTION 2-Hour Storm Depths based on Douglas County Storm Drainage Design and Technical Criteria for Basins 10 to 20 square miles for Zone 1-HR STORM EVENT DISTRIBUTION 2 - Yr Storm Event, Durations Less than 1-hr "Short duration rainfall relations for the Western United 6-Hour Design Storm - TIME Cumulative Depth (MIN) 5-yr 1 OO-yr 185 0.922 1.771 190 0.939 1.802 195 0.951 1.826 200 0.965 1.853 205 0.979 1.879 210 0.993 1.906 215 1.006 1.932 220 1.019 1.956 225 1.029 1.975 230 1.040 1.997 235 1.051 2.018 240 1.063 2.040 245 1.075 2.064 250 1.086 2.086 255 1.097 2.107 260 1.104 2.119 265 1.115 2.141 270 1.126 2.162 275 1.134 2.177 280 1.143 2.194 285 1.150 2.208 290 1.159 2.225 295 1.168 2.242 300 1.176 2.258 305 1.185 2.275 310 1.193 2.290 315 1.200 2.304 320 1.209 2.321 325 1.216 2.335 330 1.224 2.350 335 1.231 2.364 340 1.238 2.376 345 1.243 2.386 350 1.247 2.395 355 1.250 2.400 360 I 1.250 2.400 6-Hour Design Storm - TIME Cumulative Depth (MIN) 5-Yr 100- Yr 5 0.013 0.024 10 0.019 0.036 15 0.025 0.048 20 0.034 0.065 25 0.040 0.077 30 0.050 0.096 35 0.057 0.110 40 0.066 0.127 45 0.075 0.144 50 0.085 0.163 55 0.096 0.185 60 0.106 0.204 65 0.116 0.223 70 0.128 0.245 75 0.140 0.269 80 0.153 0.293 85 0.165 0.317 90 0.180 0.346 95 0.196 0.377 100 0.211 0.406 105 0.235 0.451 110 0.255 0.490 115 0.300 0.576 120 0.363 0.696 125 0.450 0.864 130 0.529 1.015 135 0.613 1.176 140 0.690 1.325 145 0.757 1 .454 150 0.784 1.505 155 0.810 1.555 160 0.828 1.589 165 0.850 1.632 170 0.872 1.675 175 0.888 1.704 180 0.905 1.738 TIME 2-Hour Design Storm - Cumulative Depth (MIN) 2-Yr 5-Yr 10-Yr 50-Yr 1 00- Y r 0 0.000 0.000 0.000 0.000 0.000 5 0.014 0.021 0.025 0.023 0.021 10 0.043 0.060 0.072 0.085 0.082 15 0.104 0.151 0.175 0.174 0.176 20 0.219 0.312 0.364 0.317 0.340 25 0.399 0.574 0.679 0.584 0.627 30 0.500 0.711 0.830 1.029 1.140 35 0.545 0.772 0.901 1.242 1 .427 40 0.581 0.818 0.955 1.385 1.591 45 0.603 0.856 1.003 1.474 1.718 50 0.624 0.894 1.043 1.563 1.820 55 0.646 0.925 1.084 1.620 1.902 60 0.667 0.957 1.124 1.677 1.984 65 0.689 0.988 1.164 1.734 2.066 70 0.703 1.020 1.205 1.776 2.107 75 0.718 1.046 1.245 1.819 2.148 80 0.732 1.069 1.276 1.851 2.173 85 0.747 1.092 1.300 1.883 2.198 90 0.761 1.115 1.324 1.908 2.222 95 0.775 1.138 1.348 1.933 2.247 100 0.790 1.154 1.372 1.958 2.271 105 0.804 1.170 1.396 1.983 2.296 110 0.819 1.185 1 .420 2.008 2.321 115 0.826 1.201 1 .441 2.033 2.345 120 0.833 1.215 1 .458 2.058 2.370 hr Storm Event, Durations Less than 1-hr .... rainfall relations for the Western United ichards TIME 1-Hour Design Storm - Cumulative Depth (MIN) 2-Yr 5-Yr 10- Yr 50-Yr 100- Yr 0 0.000 0.000 0.000 0.000 0.000 5 0.238 0.347 0.416 0.516 0.595 10 0.389 0.567 0.680 0.819 0.943 15 0.468 0.683 0.819 1.050 1.210 20 0.511 0.746 0.895 1.181 1.360 25 0.554 0.809 0.970 1.311 1.510 30 0.598 0.872 1.046 1 .442 1.661 35 0.618 0.901 1.082 1 .498 1.725 40 0.638 0.931 1.117 1.555 1.790 45 0.659 0.961 1.153 1.611 1.855 50 0.679 0.991 1.189 1.667 1.920 55 0.700 1.020 1.224 1.724 1.985 60 0.720 1.050 1.260 1.780 2.050 hr 1 1 Depth 30 min 0.83 Depth 30 min 0.81 From States", Arkell and Richards Ratios to 1-Hr Storm Point Rainfal 5 min 0.65 and Storm Point Rainfal - - 10 min 5 min - - 0.46 0.59 o min 0.54 100 - Yr From "Short duratio,. States", Arkell Ratios to 1-Hr 5min 0.29 5 min 0.33 .;, "\ . l~ ~' "\ ;i