Reference Documents - Stormwater Management Plan & Waste Management Plan - MCU26/0040, OPW26/0066 & RAL26/0013 (As Published)

4.5    WBNM Analysis Post-Development, Unmitigated Scenario

Peak flow rates, for the post-development scenario without any intervention measures, were
generated by WBNM to provide a comparison to the pre-development runoff. The table below
shows peak discharge in all storm events for the unmitigated post-development scenario,
including a difference comparison to the pre-development scenario.



                                           DEVELOPED CASE - LPOD1
                                                  Peak Flow Rates - Q (m3/s)
                          AEP             EXISTING       DEVELOPED        Difference
                         63.2%              0.197           0.493          150.3%
                          50%               0.242           0.556          129.8%
                          20%               0.457           0.748            63.7%
                          10%               0.485           0.905            86.6%
                          5%                0.578           1.072            85.5%
                          2%                0.725           1.212            67.2%
                          1%                0.801           1.347            68.2%
              Table 4-5 WBNM discharge flow rates at LPOD1 for the unmitigated post-development scenario


                                           DEVELOPED CASE - LPOD2
                                                  Peak Flow Rates - Q (m3/s)
                          AEP             EXISTING       DEVELOPED        Difference
                         63.2%              0.000           0.012             N/A
                          50%               0.000           0.013             N/A
                          20%               0.000           0.018             N/A
                          10%               0.000           0.024             N/A
                          5%                0.000           0.025             N/A
                          2%                0.000           0.026             N/A
                          1%                0.000           0.029             N/A
              Table 4-6 WBNM discharge flow rates at LPOD2 for the unmitigated post-development scenario


                                         DEVELOPED CASE - COMBINED
                                                  Peak Flow Rates - Q (m3/s)
                          AEP             EXISTING       DEVELOPED        Difference
                         63.2%              0.197           0.504          155.8%
                          50%               0.242           0.569          135.1%
                          20%               0.457           0.766            67.6%
                          10%               0.485           0.929            91.5%
                          5%                0.578           1.097            89.8%
                          2%                0.725           1.239            70.9%
                          1%                0.801           1.376            71.8%
             Table 4-7 WBNM discharge flow rates from the site for the unmitigated post-development scenario




2576-SBSMP-01_Version 2.0 (April 2026)                                                                     Page 18 of 23
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