Powells Creek Flood Study
Table 28: Results of Blockage Variation – Change in Peak Depth (m) ID
Location
Peak Flood Depth 5% AEP
Difference with 5% AEP (m) Decrease blockage by 25%
Increase blockage by 25%
Peak Flood Depth 1% AEP
Difference with 1% AEP (m) Decrease blockage by 25%
Increase blockage by 25%
H01
Pedestrian Bridge 2
0.63
0.00
0.00
0.71
-0.01
0.00
H02
Pedestrian Bridge 1
1.04
0.00
0.00
1.11
-0.01
0.00
H03
Front of community Centre
0.20
0.00
0.00
0.22
0.00
0.00
H04
Railway underpass 2 East side
0.12
0.00
0.00
0.16
0.00
0.00
H05
Railway underpass east side
0.47
0.00
0.00
0.68
0.02
0.00
H06
Railway underpass west Side
0.57
0.00
0.00
0.72
0.01
0.00
H07
7 Concord Avenue low point George Street low point near soccer field
0.44
0.01
-0.02
0.55
0.02
-0.02
0.81
0.10
-0.21
1.08
0.14
-0.18
Powells Creek @ Argonne Street Powells Creek @ Pomeroy Bridge
0.19
0.00
0.00
0.35
-0.01
-0.01
0.20
0.01
-0.01
0.29
0.00
-0.01
H11
Powells Creek @ Allen Street
1.92
0.01
-0.01
2.09
0.00
-0.01
H12
Powells Creek @ Brussels Street
0.40
0.01
0.00
0.56
-0.01
-0.01
H13
Powells Creek @ Warsaw Street
0.75
0.02
0.00
0.92
-0.02
-0.01
H08 H09 H10
An additional blockage scenario investigated was the effect of 100% blockage of the culverts under Homebush Bay Drive with the results for the 1% AEP event shown on Figure 25. The figure shows that flood levels will rise by up to 0.7m. The two main areas are: • •
between Victoria Avenue to the south and Concord Avenue to the north and the area termed Village Green surrounded by Settlers Boulevard.
9.3.3. Sea Level Rise Variations The sea level rise scenarios were found to have an insignificant effect on peak flood levels, except in the most downstream reaches of the catchment. The open channels upstream of Underwood Road and Pomeroy Street have channel inverts of 0.35 m AHD and 0.45 m AHD (respectively) and were therefore tidally affected under current tidal conditions. Under sea level rise conditions, these locations were found to have increased peak flood levels. At Pomeroy Street the increase in peak level reduces to less than 0.1m with a 0.9m increase. The attenuation of sea level rise impacts is because of the retarding effect of the downstream mangroves and the restrictive effect of bridge structures crossing the open channel.
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