17 Bottlebrush Avenue, · MCU26/0001

Figure 2-4: DRAINS model for existing catchment




This assumption is considered appropriate as the existing site is currently developed with a single dwelling and
associated impervious area consistent with low density residential conditions. The relevant DRAINS catchment
inputs are detailed in Figure 2-5.




Figure 2-5: DRAINS catchment inputs




The pre-development flow rates for various AEP were calculated using DRAINS. The results are summarized in
Table 2-3.
Table 2-3: DRAINS results for existing catchment

 AEP %                                                 63.2%        50%     20%     10%      5%      2%        1%

 Pre-Development Flow (m³/s)                           0.011        0.013   0.020   0.024   0.028   0.034    0.038

A comparative assessment was conducted to evaluate the variance between DRAINS results and the Rational
Method calculations. The differences between the two methodologies are presented in Table 2-4.




 17 BOTTLEBRUSH AVENUE, NOOSA HEADS
                                                   7 January 2026                                     P a g e |9
 Stormwater Management Plan
 Client Reference: P0433-25-001
 Prepared for Made Capital PTY LTD