Revised Stormwater Mangement Plan

65-67 Elanda Street, Sunshine Beach
Site Based Stormwater Management Plan
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3. Hydrological Modelling and Analyses
In order to identify the impact of the proposed development to the existing environment,
hydrological analyses are carried out. Based on Noosa Plan (2020), stormwater drainage
design is required to be carried out based on QUDM, hence, the following analyses and
design is performed based on the guideline of QUMD-2016.

3.1 Modelling Parameters and Strategy
Numerical modelling and analyses are developed only for stormwater impact assessment
purpose, no flood overlay assessment is analysed.

The geographical location of the development site is (27.4S, 153.04E). The rainfall
intensities for various durations of storm events from 63% AEP to 1% AEP are obtained
from the BoM, as contained in Appendix B.

XPSTORM (2016.1) is applied to perform hydrological modelling using Laurenson method.
This method allows each catchment to be split into pervious and impervious sub-areas, and
route stormwater runoff through non-linear catchment storage using separate hydrographs
from pervious and impervious portions.

The complicated surface characteristics can be simulated by nominating appropriate
Manning’s roughness for both Pervious and Impervious sub-areas. Manning Roughness
coefficient (n) are summarised in Table 3.1.

Table 3.1 Manning’s roughness summary

                                              Impervious area   Pervious area (ha)
                                                     (ha)
                Manning’s Roughness                 0.011             0.030
                            (n)



Laurenson's Method, among numerous hydrological methods, applies constant values for
Initial and Continuing Losses in considering the infiltration. Initial Loss (IL) and Continuing
Losses (CL) have been applied to the hydrological model.




File Name:            WCD-22936 – 65-67 Elanda_SWMP.docx
Revision:             E                                                                     9