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2014022_71_SeaviewTce_SWMP-revC_full · OPW16/0021
From the archive OPW16/0021- Response - Civil Plans. File date in the archive: 2016-05-16 04:05.
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existing!case!natural!catchment!divide!was!determined!to!fall!approximately!through!
the! centre! of! the! proposed! building! (Figure! 6).! ! As! such! and! in! order! to! maintain!
outlet! of! stormwater! runoff! into! the! predevelopment! drainage! pathways! it! is!
proposed! that! the! development! outlet! stormwater! runoff! into,! as! far! as! practical,!
the!same!drainage!pathways!as!the!predevelopment!case.!!!
!
Table!11:!!WBNM!SubbCatchment!Fraction!Impervious!Values!–!Developed!Scenario!
Developed!Scenario!
Existing!Scenario!
WBNM!SubbCatchment! Area!(ha)! b!Conventional!
Impervious!(%)!
Impervious!(%)!
External! 0.288! 75! 75!
D1c! 0.155! 0! 0!
D1a_Driveway! 0.026! 100! 0!
Green_Roof_North! 0.016! 100#! 0!
Green_Roof_South! 0.048! 100 ! # 0!
Lower_A_North! 0.009! 0! 0!
Lower_A_South! 0.015! 0! 0!
Lower_B! 0.057! 48! 0!
Roof! 0.022! 100! 0!
C3! 0.317! 0! 0!
Total! 1.175! ! !
#!It!is!noted!that!while!this!area!is!proposed!to!be!green!roof!it!is!modelled!for!the!
purposes! of! analysis! of! potential! increase! in! peak! flow! from! the! development! as!
100%!impervious.!
Peak! flows! tabulated! in! this! report! represent! the! peak! values! extracted! from! the!
modelled!range!of!storm!events.!!
Table!12:!!Developed!Scenario!WBNM!Outlet!Peak!Flows!–!Outlet!1!
Developed!
Existing!Peak! Change!in!Peak! %!increase!in!Peak!
!! Flow!(m3/s)!
Conventional!Peak!
Flow!(m3/s)! Flow!
Flow!(m3/s)!
2!year! 0.19! 0.19! 0.00! 0%!
5!year! 0.24! 0.25! 0.01! 1%!
10!year! 0.27! 0.28! 0.01! 1%!
20!year! 0.31! 0.32! 0.01! 1%!
50!year! 0.33! 0.33! 0.00! 0%!
100!year! 0.37! 0.37! 0.00! 0%!
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! ! ! 17!
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