8. Volume 5 - Stormwater Management Plan

                                         LAMBERT & REHBEIN
                                             ENGINEERS • MANAGERS • SCIENTISTS



3.0     STORMWATER QUANTITY

3.1     METHODOLOGY
In order to determine the stormwater flows for the site an XPStorm model of the catchments was
developed. The development layout utilised in the modelling is as shown on the preliminary
architectural plans prepared by Thomson Adsett enclosed in Appendix B. A breakdown of the
existing and proposed catchments is presented in Table 1 below.
                            Table 1 Development Catchment Area
                    PRE DEVELOPMENT                       POST DEVELOPMENT
                                               CATCHMENT A                  CATCHMENT B
IMPERVIOUS               990 m2                     2086 m2                       140 m2
PERVIOUS                1438 m2                     102 m2                        100 m2
    TOTAL               2428 m2                     2188 m2                       240 m2


The impervious area of the site will increase due to the increased roof and pavement areas
compared with the existing pre development surfaces. As such there is likely to be an increase in
stormwater runoff from the developed site. Noosa Council requires that existing levels of
stormwater discharge are maintained from the proposed development site. The stormwater
detention, if required will be designed to attenuate peak flows for all design storms up to and
including a Q100 storm.

3.2     STORM EVENTS
Q1, Q2, Q5, Q10, Q20, Q50 and Q100 were modelled for the following durations:

•       STORM 1 - 10 minutes;                       •         STORM 5 – 60 minutes;
•       STORM 2 - 15 minutes;                       •         STORM 6 – 90 minutes; and
•       STORM 3 - 30 minutes                        •         STORM 7 – 120 minutes.
•       STORM 4 – 45 minutes;
The above storms can be related to the output hydrographs presented in Appendices D & E.




 Ref: B16239CR002                           - 3 -                          Stormwater Management Plan
                                                                        Noosa Energy Centre - Noosaville