Appendix C MUSIC Modelling - planning.nsw.gov.au › - › media › Files › DPE › Plans-and-… · calculated based on the filter area requirements plus allowances for earthworks,

Appendix C

MUSIC Modelling

East Leppington - Water Cycle Management Report

Prepared for Department of Planning & Infrastructure

9 May 2013 Cardno (NSW/ACT) Pty Ltd Page C.1

C.1 Aims

The aims of the catchment based water quality modelling were to assess the:

� Impacts of the proposed development on stormwater quality; and

� Estimate the sizes of the stormwater quality improvement measures.

The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) version 5 was used for water quality assessments.

C.2 MUSIC Model Parameters The following model parameters were adopted for assessment purposes.

Rainfall Data Daily rainfall data was purchased from the Bureau of Meteorology for the nearest daily rainfall station 67015 Bringelly. The daily rainfall data between 01/01/1998 and 01/01/2008 (10 calendar years) was adopted.

Table C.1 Rainfall Details

Station No. 67015

Location Bringelly at Marylands

Data period available 01/01/1867-31/12/2008

Data period used 01/01/1998 and 01/01/2008

Data type Daily

No of years 10

Average Annual (mm) 596.9

Mean Annual Rainfall (mm) 50th%ile 640.7

Wet Year Rainfall (mm) 90th%ile 929.86

Dry Year Rainfall (mm) 10th%ile 494.88

Potential Evapo-Transpiration (PET) Data

The monthly PET data that was adopted in this study are listed in Table C.2 and represent typical PET for

areas of Western Sydney.

Table C.2 Average Daily Potential Evapo-Transpiration by Month (mm)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

5.6 5.0 4.0 3.1 2.1 1.7 1.8 2.6 3.7 4.6 5.2 6.0




Figure C.1 Comparison of Monthly Average Rainfall and Potential Evapo-Transpiration

A comparison of average monthly rainfall recorded and average monthly PET is presented in the following

Figure. C.1.

Rainfall and Runoff Parameters

The following rainfall and runoff parameters have been used:

Parameter Urban

Impervious Area Properties

Rainfall Threshold (mm/day) 1

Pervious Area Properties

Soil Storage Capacity (mm) 170

Soil Initial Storage (% of Capacity) 30

Field Capacity (mm) 70

Infiltration Capacity coefficient - a 200

Infiltration Capacity exponent - b 1

Groundwater Properties

Initial Depth (mm) 10

Daily Recharge Rate (%) 25

Daily Baseflow Rate (%) 5

Daily Deep Seepage Rate (%) 0




Fraction Impervious

For the purpose of analysis, an overall average fraction impervious was determined based on the proposed

development layout and fraction impervious per land use as outlined in Campbelltown Council’s DCP. The

spatial distribution of the landuse categories analysed when estimating the average fraction imperviousness

are plotted in Figure C.2.

The adopted fraction imperviousness for each landuse category, total area of each landuse and the resulting

overall average imperviousness is summarised in Table C.3. The resulting overall fraction impervious

equated to 0.68. For the purpose of analysis, an overall average fraction impervious of 0.7 for the

development was adopted.

Figure C.2 Land Use Categories for Determination of Average Fraction Impervious




Table C.3 Fraction Impervious by Land use Category

Land Use Fraction

Impervious

Total Area

(m2)

Impervious

Area (m2)

Low Density Residential 0.8 2,434,588 1,947,670

Medium Density Residential 0.9 461,858 415,672

Large Lots/Very Low Density 0.3 204,152 61,245

Open Space 0.1 659,364 65,936

Educational Uses 0.8 39,353 31,482

Community Uses 0.8 7,658 6,126

Local Centre 1.0 9,918 9,918

Neighbourhood Centre 1.0 15,657 15,657

Roads 1.0 156,091 156,091

Total 0.68 3,988,639 2,709,799

Pollutant Generation

MUSIC model default Event Mean Concentration (EMC) values for storm flows and base flows were used.

Treatment Measures – Bio-retention

Estimation of the size of bio-retention measures was undertaken to achieve best practice reduction targets for

Gross Pollutants (90%), Total Suspended Solids (85%), Total Phosphorous (65%) and Total Nitrogen (45%)

respectively. The adopted properties of bio-retention measures are as given in Table C.4.

Table C.4 Adopted Properties of Bio-retention Measures

Parameter Values

Low flow By-pass (m3/s) 0

High flow By-pass (m3/s) 100

Filter Depth (m) 0.65

Extended Detention Depth (m) 0.30

Filter median particle diameter (mm) 0.24

Hydraulic Conductivity (mm/hr) 120

Outlet Properties (m) 2yr ARI basin outlet width




C.2 MUSIC Model Results

MUSIC Model

The layout of the MUSIC model is given in Figure C.3.

Overall Results

It was found that a bio-retention filter area of approximately 0.5% of total catchment area is sufficient to meet

the best practice management targets for stormwater quality improvement. The overall MUSIC model results

are summarised in Table C.5.

Table C.5 Overall MUSIC Model Results

Parameter Source Load Residual Load Reduction (%)

Flow (ML/yr) 1,570 1,550 1.6

Total Suspended Solids (kg/yr) 295,000 22,700 92.3

Total Phosphorus (kg/yr) 625 218 65.1

Total Nitrogen (kg/yr) 4,400 1,800 59.1

Gross Pollutants (kg/yr) 51,700 0.00 100.0

Basin Sizing – Bioretention

Bioretention basins are located in the floodway of the ILP as shown in Figure C.4. The size of the basins was

calculated based on the filter area requirements plus allowances for earthworks, drainage and ancillary works.

As shown in Table C.6, on average the area of basins in the ILP is 3.3 times the filter area estimated by

MUSIC modelling.

A concept layout of a bio-retention basin is given in Figure C.5.




Table C.6 Estimated Filter Areas and Basin Areas

ILP Basin ID Filter Area (m2)

A

ILP Area (m2) B

B / A

BR1 316 2830 9.0

BR2 / BR3 1060 6770 6.4

BR4 133 5860 44.1

BR5 286 3610 12.6

BR6 520 1840 3.5

BR7 171 1810 10.6

BR8 447 3470 7.8

BR9 943 2035 2.2

BR10 901 3240 3.6

BR11 438 3000 6.8

BR12 653 3550 5.4

BR13 525 1090 2.1

CLB1 441 1770 4.0

CLB2 142 4180 29.4

CLB3 365 1650 4.5

CLB4 344 2090 6.1

CLB5 293 2610 8.9

CLB6 1038 1870 1.8

CLB7 978 1700 1.7

CLB8 269 2060 7.7

Total 10,263 57,035 5.6




Figure C.3 MUSIC Model Layout




Figure C.4: Sub-catchment and Bio-retention Basin Layout




Figure C.5 Concept Layout of Bio-retention Basin

11 April 2013 Cardno (NSW/ACT) Pty Ltd Page 3

Appendix D

WQM Implementation Plan

Documents

Appendix C MUSIC Modelling - planning.nsw.gov.au › - › media › Files › DPE › Plans-and-… · calculated based on the filter area requirements plus allowances for earthworks,