1. SEWERFIX WET WEATHER ALLIANCE
www.sydneywater.com.au/majorprojects
Technical Note
DATE 25/09/08 SUB PROJECT
Recalibration of East Esplanade Sub-
catchment
SUBJECT Northern Beaches Catchment Planning
Document No. NB SO-TN-001
Prepared by Faruk Kader
Reviewed by Glenn McDermott
BACKGROUND
The Manly SCAMP model was originally built and calibrated in 2001. The model was recalibrated
in 2004 following the recommendations of 2002 Needs Assessment Report to investigate the high
overflow frequency of four weirs in the Manly local government area. The recalibration of the model
used a new set of dedicated gauging data of 2004 and the subsequent analysis led to a realistic
assessment of the overflow frequency of the weirs far lower than that predicted by the 2001 model.
In 2007, SWC initiated a flow gauging program for the East Esplanade part of Manly SCAMP. The
data collected from this program was planned to be used to refine its calibration at sub-catchment
level for validation of the overflow frequency of the East Esplanade weir, located at the junction of
the Stuart St and East Esplanade RD. Figure 1 shows the East Esplanade sewer catchment and
flow gauging stations installed in 2007.
Accordingly, this modelling exercise was undertaken with the following objectives:
• To calibrate the East Esplanade sewer catchment model against the flow data gauged at three
locations, 8MAN58, 8MAN64 and 8MAN63, for the period Dec 2007-Aug 2008.
• To validate the wet weather parameters of the sewer catchment
SCOPE
• Extract East Esplanade sewer catchment model (MYN1) part from the previously calibrated
Manly SCAMP model (MYN)
• Extract and prepare model input data – rainfall, flow and outlet water level boundary data
• Analyse gauged flow data
• Select suitable dry and wet weather events for model calibration
• Calibrate the model for dry weather events
• Calibrate the model for wet weather events
2. • Validate the wet weather parameters
Figure 1: East Esplanade Sewer Catchment and Flow Gauging Stations
8MAN64
8MAN58
8MAN63
East Esplanade Overflow Weir
Flow Gauging Station
MODEL INPUT DATA
SWC installed three gauges (8MAN63, 8MAN64 and 8MAN58) to capture sufficient number of wet
weather events for use in calibration of the model, as shown in Figure1. Out of these, 8MAN58 is
located very close to the outlet of the sewer catchment to NSOOS. These three were all HVQ
stations, however, the most upstream gauge 8MAN63 was constricted.
Two closest permanent SWC rain gauges, 566100 (North Head STP) and 566089 (Manly CC),
were used to generate virtual rainfall time series data for East Esplanade for the gauging period:
The data of these two were found well correlated. Due to proximity of 566100 to East Esplanade,
this rain gauge was given more weightage in generating the data.
The following two dry weather and four wet weather events were considered for use in the model,
meeting SWC criteria as far as possible.
• Dry Weather Event 1 (DWE1): 06/05/2008 to 13/05/20008
• Dry Weather Event 2 (DWE2): 28/06/2008 to 05/07/20008
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3. • Wet Weather Event 1(WWE1): 01/02/2008 to 13/02/2008
• Wet Weather Event 2(WWE2): 02/06/2008 to 11/06/2008
• Wet Weather Event 3(WWE3): 24/07/2008 to 02/08/2008
• Wet Weather Event 4(WWE4): 08/04/2008 to 11/04/2008
In the absence of continuous measured data, the outlet water level boundary conditions for the
East Esplanade model on NSOOS at Ashburner St (820001) was generated by correlation
between this gauging station and 820002 (Eustace St), which had continuous data.
Analysis of the captured flow data was done and a summary of flow analysis for the dominant
storm of the full/whole wet weather events is provided in Table 1.
Table 1: Summary of Flow Analysis
EVENTS
DWE1 DWE2 WWE1 WWE2 WWE3 WWE4
Gauge
Daily
Flow
(Kl/d)
Peak
Flow
l/s
Daily
Flow
(Kl/d)
Peak
Flow
l/s
Daily
Flow
(Kl/d)
Peak
Flow
l/s
Daily
Flow
(Kl/d)
Peak
Flow
l/s
Daily
Flow
(Kl/d)
Peak
Flow
l/s
Daily
Flow
(Kl/d)
Peak
Flow
l/s
8MAN63 226.0 11.97 197.0 11.03 1104.0 38.08 737.0 25.23 843.0 28.81 317.0 14.70
8MAN64 708.0 22.22 847.0 25.87 2741.0 81.22 2421.0 63.74 2940.0 83.81 1426.0 50.66
8MAN58 1005.0 29.25 1004.0 33.07 3406.0 100.17 2462.0 64.15 3098.0 83.81 1677.0 54.67
Almost identical flows monitored at 8MAN64 and 8MAN58
Significant flow difference between 8MAN64 and 8MAN58
Analysis shows that the water balance between 8MAN64 (u/s) and 8MAN64 (d/s) is not consistent
during the wet weather events. The flow volume difference between 8MAN64 and 8MAN58 is
significant during event WW1; 8MAN64 recorded 20% less volume than 8MAN58, while the flow
volume difference is 2 to 5% for events WW2 and WW3. An earlier investigation found problem in
gauging of 8MAN64 before March 2008 covering event WW1. Therefore, WW1 event was not used
for calibration of the sub-catchment gauged by 8MAN64.
For its catchment area, the flow captured at 8MAN63 looks less than expected. However, the
model results show that a major component of the flow from the upstream bypasses this gauge via
a bifurcation to the downstream gauge 8MAN64.
CALIBRATION
The East Esplanade model was basically calibrated for dry periods only. To arrive at a satisfactory
flow calibration during dry period, residential flow data of 140 to 150 l/EP/D was used. The existing
wet weather parameters were able to match flow volume, flow peak and flow depths within a
reasonable range of variation. Minor adjustment of pipe roughness was done upstream of flow
gauges to improve depth calibration. Given the uncertainty in flow data, it was deemed not
worthwhile to refine the existing wet weather parameters. Calibration results are summarized in
Table 2 below, while calibration plots are provided in Appendix.
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Table 1: Summary of Calibration Results
8MAN63 (Constricted) 8MAN64 8MAN58Event
RQV RQP R R R R R R R R RQm DP DM QV QP Qm RDP DM RQV RQP Qm RDP DM
DWE1 0.98 0.60 0.98 NA NA 1.16 0.89 1.16 0.79 0.85 0.96 0.79 0.96 0.70 0.70
DWE2 1.17 0.71 1.17 NA NA 1.00 0.75 1.00 0.70 0.73 0.99 0.72 0.99 0.66 0.69
WWE1 0.61 0.67 0.61 NA NA 0.87 0.96 0.87 0.72 0.78 0.77 0.87 0.77 0.95 1.05
WWE2 0.80 0.77 0.80 NA NA 0.82 0.87 0.82 0.74 0.72 0.94 0.99 0.93 0.98 1.00
WWE3 0.89 0.89 0.89 NA NA 0.85 0.95 0.85 0.77 0.74 0.94 1.09 0.94 0.96 0.93
WWE4 1.33 1.13 1.33 NA NA 1.01 1.09 1.01 0.86 0.82 1.04 1.17 1.04 1.05 0.90
Note
RQV= Simulated Volume/Gauged Volume
RQP =Simulated Highest Peak Flow/Gauged Highest Peak Flow
RQM =Simulated Mean Flow/Gauged Mean Flow
RDP =Simulated Peak Flow Depth/Gauged Peak Flow Depth
RDM= Simulated Mean Flow Depth/Gauged Mean Flow Depth
The above ratios for wet weather events represent flow statistics for the dominant storm event within the whole storm event consisting of a number of bursts/events
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CONCLUSIONS
It appears that the existing wet weather parameters for the East Esplanade part of the Manly SCAMP
are still valid within the allowable margin of error.
Prepared: Faruk Kader (SWWA) Date:
Checked:
Glenn McDermott
(SWWA) Date:
Approved: (SWC) Date:
Comments:
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APPENDIX
Calibration Plots for Dry Weather and Wet Weather Events
7. SEWERFIX WET WEATHER ALLIANCE
Calibration Plot of Gauge 8MAN63 for DWE1
Calibration Plot of Gauge 8MAN63 for DWE2
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8. Calibration Plot of Gauge 8MAN64 for DWE1
Calibration Plot of Gauge 8MAN64 for DWE2
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