RFI - P0478-26-001_45_Maple_Street_Cooroy_SWMP

     •    Surface roughness and vegetation cover, which influence flow resistance and travel time

     •    Topographic gradients, confirming alignment between flow velocities and assumed conditions

     •    Site hydraulic connectivity, including potential depressions or ponding areas, verifying the
          appropriateness of the adopted Tc.




Figure 3-2 Max Overland Flow Path (QLD Globe, 2026)




Figure 3-3: Overland Sheet Flow Times (QUDM, 2016)




The impervious fraction for the site was determined to be 8.46%, based on a manual measurement of the total
impervious area to accurately represent existing site conditions in accordance with QUDM methodology. Lot 15 on
C5605 consists of a single dwelling and a shed, Lot 18 on C5605 is currently a vacant lot with an access driveway
partially entering the lot.

Using QUDM Table 4.5.4, the C₁₀ was determined based on the 1-hour, 10 % AEP rainfall intensity of 70.2 mm/hr.
Applying this methodology, a C₁₀ value of 0.70 was derived, as summarised in Table 3-1.

 45 MAPLE STREET, COOROY
                                               24 June 2026                                         P a g e |7
 Stormwater Management Plan
 Client Reference: P0478-26-001
 Prepared for Myall Rise PTY LTD