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

Despite this, Sydney Harbour supports a number of endangered species,
communities and migratory species (Sydney Harbour Catchment Water Quality
Improvement Plan, Sydney Metropolitan Catchment Management Authority, 2010) as
confirmed through the biodiversity search results contained in Appendix J.
The principal environmental value for Sydney Harbour Catchment (contained within
the water quality improvement plan) is maintaining a healthy ecosystem, whilst
realising the harbour’s commercial and recreational uses. The Sydney Metropolitan
Catchment Management Authority has implemented measures to combat the
catchment’s poor water quality. These measures include stormwater management
plans, stormwater re-use plans and the Sydney Harbour catchment water quality
improvement plan (Sydney Metropolitan Catchment Management Authority, 2011),
which includes defined water quality objectives established for protecting:
Aquatic ecosystems
Visual amenity
Primary (in water) and secondary (on water) contact recreation
Aquatic foods (aquaculture).
Surface water
The proposal footprint does not contain any surface water features. Any historic
surface watercourses have been diverted below ground (refer to section 6.3.2).
Sydney Harbour is the nearest surface water feature, located approximately
500 metres north of the proposal footprint. As noted above, city’s stormwater and
road runoff within the study area typically drains to the harbour generally
unattenuated. The proposal footprint is therefore hydraulically connected to the
harbour creating a potential pollution pathway. The next nearest surface water body
is Alexandra Canal, located approximately two kilometres south of the southern limit
of the proposal footprint. The canal drains to the Cooks River/Botany Bay Catchment
to the south. There is no hydraulic connection or relationship between the canal and
the proposal footprint.
Flood risk
The proposal footprint spans two established flood catchments; City Area and Darling
Harbour. City of Sydney has produced draft flood studies covering both catchments
(City of Sydney, 2014). Both studies have used historic flood data to model impacts
over the flood catchments under various scenarios. This has identified locations
prone to flooding, the depth of that flooding, and in the case of the City Area, the time
it would take for the flooding to occur after a significant rainfall event.
Four conclusions can be drawn from the draft flood studies:
Parts of the proposal footprint have flooded previously (refer to Table 6-49)
The flooding potential responds to the local topography therefore the low points
of the proposal footprint have a greater flood potential
The method of flooding varies across the catchment and is typically a
combination of overland flooding, overtopping, backup through the sewerage or
stormwater drainage systems, or groundwater levels rising up and causing
basement flooding
There is only a short period following a heavy rainfall event before certain of the
streets would start flooding.
Table 6-49 describes the general characteristics and flood risks associated with each
catchment and any key work sites at risk of flooding.
Sydney City Centre Capacity Improvement 366
Review of Environmental Factors