sydney-city-centre-review-of-environmental-factors

Table 6-49
Work sites
Flood catchment characteristics and flood risk
Flood catchment characteristics
City area
NW2: King Street
R2: Market Street
R5: York Street
F1: Macquarie Street
F2: Macquarie Street
Darling Harbour
S3: Pitt Street
S4: Ultimo Road
C1: Wentworth
Avenue
The catchment covers parts of the city centre, Millers Point and
Barangaroo. The majority of the catchment drains to Sydney
Cove via Sydney Water’s main trunk drainage system. This
includes road drainage. There are no open-channel reaches in
the catchment and water infiltration is limited due to the
extensive impervious surfaces. The catchment has flooded six
times since 1949.
The draft catchment flood study (BMT WBM Pty Ltd, 2014a)
predicted flooding across a range of scenarios including the
probable maximum flood (PMF) event (eg worst case flood
risks) in the following areas within the construction footprint:
Along the length of King Street (work site NW2) to a depth
of over one metre between George Street and Pitt Street
Along the length of Market Street (work site R2) to a depth
of 0.5 metres
Along a small section of York Street (work site R5) to a
depth of 0.1 metres
Along sections of Macquarie Street (work sites F1 and F2)
to a depth of 0.1 metres
The study also provisionally reports that there would be a
minimum of 25 minutes following an extreme rainfall event
before some of the city streets would start to flood.
The catchment covers Haymarket, Ultimo and parts of the city
centre. The catchment drains broadly south to north via Sydney
Water’s main trunk drainage system. The following relevant
flood risks are noted in the draft flood study (BMT WBM Pty
Ltd, 2014b):
The corner of Goulburn Street and Wentworth Avenue
(work site C1) which was subsequently modelled and
shown to flood to 0.3 metres under a PMF worst case
event
The corner of Ultimo Road and Harris Street (work site S4)
which was subsequently modelled and shown to flood to
0.6 metres under a PMF worst case event
The ability for Pitt Street at Liverpool Street (work site S3)
was shown to flood under a PMF worst case event.
With this knowledge, City of Sydney is currently in the process of developing a flood
risk management strategy for the catchment based on the predicted flood levels.
Groundwater
Sydney’s groundwater is classified into three principal aquifer units: the Botany Bay
sand beds; the metropolitan coastal sand (coastal sands); and the Sydney basincentral
(porous) rock beds.
Sydney City Centre Capacity Improvement 367
Review of Environmental Factors