20517 App J.pdf [As Published] · 132007.1259

Concept Stormwater Management Plan

Essence of Peregian

The relevant mean yearly rainfall for the 100 year period of available data for the Tewantin station was found to
be 1681mm. The yearly rainfall data was then analysed to determine which consecutive 30 year average was
closest to the average of the entire data set. This was determined to be the period from 1938 to 1967. Within this

period, a 10 and 90 percentile rainfall year for the total 100 year period also occurs.

Table 5.1 compares the 100 year period and the 30 year period relevant parameters.

Table 5.1: Comparison of 100 & 30 Year Periods

 

 

 

 

 

 

 

Parameters Compared 100 year period (mm) 30 year period (mm)
Mean 1681 1683
10%ile 1184 (1187mm for 1940) | 1247 (1254mm for 1951)
90%ile 2184 (2183mm for 1950) | 2262 (2260mm for 1956)

 

 

 

Note: Rainfall data from Tewantin Post Office was not used for MUSIC Modelling as it had limited pluviograph data.

5.3.2 Roof Details and Irrigation Areas

Data input into the simulation was as follows:

e Coefficient of Runoff value of 0.9 was used as per HB 230 — 2006: Rainwater Tank Design and
Installation Handbook;

e 100% roof area capture of rainfall for the beach shacks, as rainwater tanks are proposed at either end
of each beach shack to capture runoff from multiple roof pitches. The amount of rainwater used for a
single beach shack was multiplied by thirty to obtain the total annual water savings; :

e 100% roof area capture of rainfall from accommodation buildings due to the proposal for underground
tanks for these buildings;

e Each of the three pairs of accommodation buildings (Refer Section 5.2) have surrounding landscaped
areas that are proposed to be irrigated by the captured rainwater from their respective underground
tank.

Further details of roof areas and irrigation areas are provided in Appendix D.
5.3.3 Usage

As stated in Section 4.3.4, the water usage rate of 240 L/person/day has been adopted for beach shack occupants.
This is the reduced target usage adopted by MSC. An average household occupancy of 2.5 persons was adopted.
Therefore, the daily beach shack water use input into the simulation was 600 L/day. A breakdown of total water
usage was sourced from the Integrated Water Management Guidelines (Version 1), and is presented in Table 5.2
along with Rainwater Tank usage. :

Table 5.2: Breakdown of Total Water Usage

 

 

 

 

 

 

 

 

 

 

Use Proportion of Total Use Rainwater Tank Use
(Liday)

External 30% Not applied
Toilets 20% 120
Laundry 15% 90

Hot water 20% Not applied
Kitchen / Bathroom 15% ~ Not applied
Total 100% { = 600 L) 210

 

 

Seasonal occupancy rates for Holiday Units of Noosa Southern Beaches were then applied fo the Rainwater Tank
Use (Office of Economic and Statistical Research, 2006). These occupancy rates are shown in Table 5.3 below.

 

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