Attachment C - Stormwater Management Plan - 30-32 Doonella Street_SMP-revA_full (00016826)

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3.2       Rational!Method!Calibration!
The!existing!scenario!WBNM!model!has!been!calibrated!to!Rational!Method!derived!
peak!flows!at!the!outlet!of!the!catchment!draining!to!the!Doonella!Street!frontage.!!!
A! summary! of! the! Rational! Method! calculation! is! provided! below! in! Table! 9! and!
additional!details!of!the!Rational!Method!calculation!are!provided!in!Appendix!2!of!
this!report.!
Table!9:!Rational!Method!Calibration!Summary!(Total!Catchment)!

                 Parameter!                                                   Value!
                 Time!of!Concentration!(tc)!!                              !5!minutes!
                 Catchment!Area!                                        0.2527!hectares!
                 C10!Value!                                                     0.7!
                 100!year!Rainfall!Intensity!(6!minute!duration)!          321!mm/hr!
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A! comparison! of! peak! Rational! Method! flow! rates! compared! with! peak! WBNM!
model!flow!rates!are!provide!in!Table!10!below.!
Table!10:!Rational!Method!Peak!Flows!Versus!WBNM!Peak!Flows!!

                      1yr!ARI!   2yr!ARI!   5yr!ARI!        10yr!ARI! 20yr!ARI! 50yr!ARI! 100yr!ARI!
    Catchment!                              (m3/s)!
                      (m3/s)!    (m3/s)!                     (m3/s)!   (m3/s)!   (m3/s)!   (m3/s)!
     WBNM!             0.08!      0.10!         0.12!         0.14!     0.16!     0.16!     0.18!
     Rational!         0.05!       0.07!        0.09!        0.11!      0.13!          0.16!   0.19!
%!Difference!          33.0!       29.3!        22.8!        18.8!      15.8!          "1.7!   "5.1!
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The! above! results! show! that! a! reasonable! peak! flow! calibration! has! been! achieved!
from! the! WBNM! model! when! compared! to! a! Rational! Method! calculation.! ! The!
WBNM!model!produces!a!higher!peak!in!the!smaller!events,!however,!this!would!be!
considered!acceptable!in!assessing!non"worsening!of!flows.!
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