1909-13367 SRA referral response approved docs

Prebursts have not been deemed appropriate for urban and semi-urban situations as their use can
produce anomalies in the results.
Rainfall Temporal Patterns

XPStorm has incorporated the temporal patterns from ARR DataHub for the given site location (-26.445,
152.897) on the 20 June, 2019).

These temporal patterns have been used to determine the critical storm duration for each of the design
events 1% to 1EY.


3. 2     P ropo s ed D ev e lop ed Si t e D r ain ag e

The proposed development comprises 245 relocatable dwellings with a shared clubhouse. The
developed case results in an increased impervious area and decreased proportion of pervious
landscape area.

The site consists of three sub catchments. Each sub catchment will be directed to one of three LPOD.
Catchment 1 will be captured and directed to LPOD 1, while catchments 2 and 3 will be directed to
LPOD 2 and 3.

Table 2 below details the developed catchment characteristics. Refer Appendix AC for the extents of
the developed catchment.

Table 2 – Developed site catchment summary

 Catchment        BioBasin Catchments 1 and 4       BioBasin Catchment 2      BioBasin Catchment 3

       Area                 59,730m2                      18,140m2                   29,450m2

     %
                           87% approx.                   87% approx.               87% approx.
 impervious

                        (LPOD 1) North of          (LPOD 2) North-East of     (LPOD 3) South-East of
 Discharge
                     Development Site (See         Development Site (See      Development Site (See
  location
                     Appendix AC for details)      Appendix AC for details)   Appendix AC for details)

       Slope                  1.5%                          1.5%                       1.5%




3. 3     E xi st i ng an d d ev e lop ed s it e comp a ri so n

The XPStorm modelling program Version 2018.1 was used to compute the above information, the
hydrological model adopted was the Laurensons Method. Figure 2 below depicts the model layout used
within XPStorm.




                                         Stormwater Management Report                                    8
S19-007                                    122 & 144 Myall St, Cooroy