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2D Gag

40 XP-—SWMM MODEL
4.1 Introduction

XP-SWMM Version 10.0 was used to analyse the stormwater runoff and drainage of the
proposed site and the proposed stormwater network.

4.2. Catchments

The catchments used for the XP-SWMM model were taken from the proposed design for
the stormwater drainage network completed in PC-Drain. Catchments that were assumed
to be only overland flow and hence not allowed for in the PC-Drain model were analysed
in the XP-SWMM Model. Catchment runoff that was assumed to be stored and treated by
the infiltration system (Qz2o from roofwater runoff) was not analysed in the model due to
the fact it would be directly stored in the infiltration system and infiltrated through the sand
layer. The Post - Development Catchment Plan can be seen in Figure 4.

4.3. Flows

The catchment flows were calibrated to match the peak flow from the 15min, 20min,
25min, 30min, 45min and 60 minute storm durations for the 100 year ARI event. It was
found that for each catchment the 25 minute storm duration was the worst case scenario
and hence produced the greatest flows and depths.

4.4 Results

The output results from the XP-SWMM model can be seen on Figure 5. It can be seen
that the proposed stormwater drainage network is more than adequate with the greatest
ponding depth achieved at any one node being 140mm. It can also be seen that the total
flow out of the site is 2.07m°/s, which is much lower than the pre-development flow of
2.80m"/s.

Table 4 _ Post - Development Quoo Flows for a storm duration of 25mins.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Post-Development Q1o9 Outlfow (m°/s) — OUT 1 0.052
Post-Development Qioo Outlfow (m°/s) — OUT 2 0.142
Post-Development Qio0 Outlfow (m/s) — OUT 3 0.129
Post-Development Q1o0 Outlfow (m°/s) — OUT 4 0.068
Post-Development Q1o9 Outlfow (m/s) — OUT 5 0.054
Post-Development Q1o0 Outlfow (m*/s) — OUT 6 0.063
Post-Development Q1o0 Outlfow (m*/s) - OUT 7/H 0.541
Post-Development Qo Outlfow (m°/s) — OUT 8/D 0.605
Post-Development Qio9 Outifow (m*/s) — OUT 9/A 0.460
TOTAL Post- Development Qioo Outlfow (m*/s) 2.114
TOTAL Pre - Development Qioo Outifow (m*/s) 2.70
Is there a Non-Worsening effect between Outflows? Yes
Noosa Domain Retirement Village, Noosaville 10 Site Based Stormwater Management Plan
M1717 Revision B 16 August, 2006