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 San Antonio
 Unified Development Code
 Appendix H. STORM WATER DESIGN CRITERIA MANUAL
 Chapter 5. HYDROLOGY
 Appendix 5.5. Rainfall Data

§ 5.5.1. Rainfall Intensity-Duration  

Latest version.

  • Use Table 5.5.1A to determine rainfall intensity.

    Table 5.5.1.A - Rainfall Intensity Duration

    TIME MINUTES FREQUENCY
    2-YEAR 5-YEAR 10-YEAR 25-YEAR 50-YEAR 100-YEAR 500-YEAR
    5 7.200 8.400 9.413 11.100 12.432 13.542 18.204
    6 6.684 7.836 8.830 10.331 11.648 12.877 17.258
    7 6.277 7.381 8.365 9.722 11.025 12.341 16.497
    8 5.944 7.009 7.982 9.224 10.512 11.894 15.864
    9 5.666 6.696 7.658 8.806 10.079 11.514 15.327
    10 5.427 6.427 7.380 8.447 9.707 11.184 14.862
    11 5.220 6.194 7.137 8.136 9.382 10.893 14.453
    12 5.038 5.988 6.923 7.862 9.095 10.635 14.090
    13 4.877 5.805 6.731 7.618 8.839 10.403 13.763
    14 4.731 5.641 6.558 7.399 8.608 10.192 13.468
    15 4.600 5.480 6.400 7.200 8.400 10.000 13.200
    16 4.458 5.296 6.159 6.959 8.088 9.551 12.765
    17 4.328 5.129 5.942 6.741 7.806 9.147 12.368
    18 4.209 4.977 5.743 6.541 7.549 8.781 12.005
    19 4.099 4.836 5.562 6.357 7.314 8.449 11.672
    20 3.998 4.707 5.395 6.188 7.098 8.146 11.364
    21 3.904 4.587 5.241 6.031 6.898 7.867 11.079
    22 3.816 4.476 5.098 5.886 6.713 7.610 10.814
    23 3.734 4.372 4.965 5.749 6.541 7.373 10.566
    24 3.658 4.275 4.841 5.622 6.380 7.153 10.335
    25 3.586 4.184 4.725 5.503 6.229 6.947 10.117
    26 3.518 4.098 4.616 5.390 6.088 6.756 9.913
    27 3.453 4.017 4.514 5.284 5.955 6.576 9.720
    28 3.393 3.941 4.417 5.184 5.830 6.408 9.538
    29 3.335 3.868 4.326 5.089 5.711 6.250 9.365
    30 3.280 3.800 4.240 5.000 5.600 6.100 9.200
    31 3.209 3.723 4.155 4.905 5.501 6.003 9.025
    32 3.142 3.650 4.074 4.814 5.407 5.911 8.870
    33 3.078 3.580 3.997 4.727 5.318 5.823 8.722
    34 3.018 3.514 3.924 4.644 5.233 5.739 8.581
    35 2.960 3.450 3.854 4.565 5.152 5.658 8.446
    36 2.906 3.390 3.787 4.490 5.074 5.581 8.317
    37 2.853 3.332 3.723 4.418 4.999 5.507 8.194
    38 2.803 3.277 3.662 4.349 4.928 5.435 8.075
    39 2.755 3.224 3.604 4.283 4.859 5.367 7.961
    40 2.709 3.173 3.548 4.219 4.793 5.301 7.852
    41 2.665 3.124 3.494 4.158 4.729 5.238 7.747
    42 2.623 3.077 3.442 4.099 4.668 5.176 7.646
    43 2.582 3.032 3.392 4.043 4.609 5.117 7.548
    44 2.543 2.989 3.345 3.988 4.552 5.060 7.454
    45 2.505 2.947 3.298 3.936 4.497 5.005 7.363
    46 2.469 2.907 3.254 3.885 4.444 4.952 7.275
    47 2.434 2.868 3.211 3.836 4.393 4.900 7.190
    48 2.400 2.830 3.169 3.788 4.343 4.850 7.108
    49 2.368 2.794 3.129 3.743 4.295 4.802 7.028
    50 2.336 2.759 3.090 3.698 4.248 4.754 6.951
    51 2.306 2.724 3.052 3.655 4.203 4.709 6.876
    52 2.276 2.691 3.016 3.613 4.159 4.664 6.804
    53 2.247 2.659 2.980 3.573 4.117 4.621 6.733
    54 2.220 2.628 2.946 3.534 4.075 4.579 6.665
    55 2.193 2.598 2.913 3.496 4.035 4.538 6.598
    56 2.167 2.569 2.880 3.459 3.996 4.499 6.534
    57 2.141 2.541 2.849 3.423 3.958 4.460 6.471
    58 2.117 2.513 2.819 3.388 3.921 4.422 6.410
    59 2.093 2.486 2.789 3.354 3.885 4.386 6.350
    60 2.070 2.460 2.760 3.320 3.850 4.350 6.300
    120 1.285 1.555 1.775 2.175 2.550 2.900 4.050
    180 0.933 1.140 1.317 1.633 1.900 2.200 3.133
    360 0.552 0.668 0.767 0.950 1.083 1.250 1.767
    720 0.315 0.383 0.450 0.533 0.625 0.733 1.033
    1440 0.185 0.223 0.250 0.313 0.375 0.417 0.571