Appendix B - Amended Biome Consulting Response

3.1.2     INFILTRATION LOSS & LAG PARAMETERS

Infiltration Loss and Lag Parameter values were adopted as per Water Technology’s Cooroy Flood Study (Report No.
J2835-01_R02v01 dated 26 July 2013), which covers the Cooroy region and site area. A parameter summary is provide
in Table 3-2 below.

                                 Table 3-2:   XP-RAFTS Calibration Parameter Summary

                    XP-RAFTS Model Parameter                       Value From Cooroy Flood Study

              Storage multiplication co-efficient Bx                                1

              Pervious Initial Rainfall Loss (mm)                                   10

              Pervious Continuing Rainfall Loss (mm/hr)                             2.5



Impervious Initial and Continuing Loss values were conservatively assumed as 0mm.

3.1.3     CHANNEL ROUTING

Channel Routing (XP-RAFTS Link Routing) was modelled as per Water Technology Cooroy Flood Study (2013). The ‘k’
lag values were determined directly based on flowpath length and average channel velocity of 0.9m/s for natural overland
flowpaths and 2.0m/s for runoff conveyed through drainage or road network. A constant ‘x’ coefficient of 0.2 was adopted
as per the Cooroy Flood Study (2013).

3.1.4     RAINFALL DATA

Rainfall data was generated based on rainfall IFD parameters provided by Water Technology’s Cooroy Flood Study
(Report No. J2835-01_R02v01 dated 26 July 2013) for the Cooroy Region.

3.1.5     EXISTING PEAKS FLOW

Modelling was undertaken for the all recurrence interval storm events up to and including the 100-year ARI storm event
with storm durations ranging from 30 to 120 minutes (these were considered the critical durations). Peak flow results for
the Existing Scenario have been provided in Table 3-3 below at the site discharge locations (i.e. Discharge Location A
and B as discussed in Section 2.3).

                                         Table 3-3:    Existing Peak Flow Results
                                        Peak Flow at Discharge         Peak Flow at Discharge
                           AEP
                                        Location A North (m3/s)       Location B Central (m3/s)
                           63%                   0.17                           1.14
                           39%                   0.26                           1.71
                           18%                   0.36                           2.54
                           10%                   0.43                           3.02
                           5%                    0.55                           3.69
                           2%                    0.66                           4.28
                           1%                    0.77                           4.95




16-001014-01B | STORMWATER MANAGEMENT PLAN                      COOROY RETIREMENT COMMUNITY, TRADING POST
(SWMP) | PALM LAKE RESORTS                                                                  ROAD, COOROY                    |8