RFI - Attachment 3 - Stormwater Management Plan

A summary of the results is included in Table 3.4 and showing the pre and post conditions at the nominated
locations through the drainage feature. Refer to Appendix C TUFLOW Modelling Flood for the flood maps
resulting from the modelling.
Table 3.4 – Pre and Post-Development Flood Depths and Depth Velocity

  Point      Existing          Existing       Developed          Developed     Existing     Existing      Developed        Developed
   ID           1%               1%           1% Critical        1% Critical     10%         10%             10%             10%
              Critical         Critical         Depth               dxV        Critical     Critical       Critical         Critical
              Depth              dxV                                            Depth         dxV           Depth             dxV
 1          0.393               0.431               0.1              0.201      0.229        0.405            0                0

 2          0.372               0.645             0.172              0.205      0.323         0.254                0             0

 3          0.311               0.453             0.111              0.194      0.194         0.388                0             0

 4          0.026               0.014             0.029              0.02       0.02           0.01                0             0

 5          0.025               0.006                0                 0          0              0                 0             0

 6          1.545               1.195             1.555              1.072      1.357         0.626           1.249           0.669

 7          2.09                1.006             2.155              0.87       2.016         0.519           1.853             0.6

 8          1.657               0.911             2.012              0.95       1.629         0.417           1.723            0.65

 9          1.455               1.502             1.788              1.849      1.043          1.25           1.537             1.4

 10         1.463               2.216              1.42              2.057      1.099         1.321           1.137           1.156

 11         1.638               2.122             1.609              1.957      1.337         1.157           1.314           1.132

 12         1.313               1.891              1.29              1.749      1.029         1.107           1.007           1.082

 13         1.514               1.833             1.511              1.748      1.328          1.15           1.312           1.103



At the location of the culvert (POI 1 to 3), the road is now trafficable during the 1% AEP storms (depth < 0.2m and
dxV <0.3m/s² as per QUDM Table 7.4.5) and unaffected under the 10% AEP storms.
Although the culvert upgrade results in increased depth of flow upstream of the crossing, the impacts are
contained within the heavily vegetated riparian buffer zone and areas of biodiversity significance overlays where
impacts are expected to be minimal. At a location 100m upstream of the culvert, the difference from the existing
flows are negligible, and downstream of the crossing there is no worsening to existing conditions. Furthermore,
the upgraded culvert also results in an improvement to flood conditions under the 10% AEP storm event with
reduced flood depths upstream and downstream of the culvert. The proposed upgrade of the culvert is therefore
unlikely to result in changes to the upstream or downstream property owners causing additional risk of significant
nuisance or hazard beyond existing conditions.




Project number 21020                                                                                                   Page 16 of 36
File RECOR Concept Stormwater Management Report - 21020.docx, 2022-09-05
Revision 0


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