How has the flooding issue been addressed?
The proposed upgrade crosses the Macleay River floodplain near
Frederickton. A detailed assessment of flooding behaviour and
the most appropriate bridging configuration was undertaken in
consultation with the flooding group, local landowners and other
stakeholders. The process to determine the optimum length of
bridging across the Macleay River floodplain involved modelling
of various bridge lengths and configurations, as well as input
from the flooding group. This included evaluation of various
lengths of partial bridging and the full bridging option. The
flood modelling assessed the characteristics of flooding during
various scenarios including the 1-in-13-year, 1-in-20-year and
1-in-100-year flood events.
Bridge configurations were assessed considering afflux (the
increase in the level of water caused by changes to the
flow behaviour), flow velocity, changes in time and depth of
flooding, capital cost, geological conditions, surrounding land
uses, heritage and potential flood damage.
Based on this modelling, the optimum length for floodplain bridging was determined to
be approximately 2.2 kilometres comprising three main bridges.
These bridges will cross the southern end of the floodplain,
South West Rocks Road and the Macleay River. There will also
be a small bridge crossing the existing highway east of Frederickton.
What adjustments have been made to the design?
The proposed route from south of Kempsey to north of Eungai Rail is shown
below. The adjustments made following
community consultation and field investigations are identified
on this plan. Further changes during the detailed design and environmental
assessment phase may occur as community discussions continue.
The main features of the design adjustments are as follows.
Floodplain bridging
The proposed floodplain bridging includes bridges over the southern floodplain
(700 metres), South West Rocks Road (790 metres), Macleay River
(660 metres) and the existing highway at Frederickton (20 metres).
The proposal allows for a 1 in 100 year levee to protect Frederickton.
The design allows 13 of the 16 remaining trees from the Anzac memorial
avenue in Ferry Lane to be retained. A management plan will
be prepared to mitigate the impact on this memorial avenue.
South Kempsey interchange
The South Kempsey interchange is located approximately 1 kilometre south
of the squash court facility. The location and design of the
interchange takes advantage of the existing terrain and provides
a visual gateway to Kempsey. It is also located away from the
majority of residences in the area.
Frederickton interchange
The Frederickton interchange has a single south-western connection to
the existing highway. This interchange layout reduces the impact of the project on the floodplain and the floodwater flow paths. This means that less bridging is needed, and there will be less impediment to floodwaters. The
design also minimises the visual impact of the interchange.
Stuarts Point Road interchange
The Stuarts Point Road interchange is a full interchange near Eungai Rail, with connections to the existing highway, Eungai Rail and Stuarts Point. It provides traffic movements similar to the existing intersection arrangements.
Alignment adjustments
The alignment of the highway was developed considering various community, environmental and engineering issues.
The alignment has changed at Pola Creek, Collombatti and Barraganyatti to address impacts on water courses, agricultural operations, threatened species and local amenity.
Crescent Head Road
Crescent Head Road is proposed to pass over the proposed highway. This
reduces the amount of soil needed for embankments and lowers the highway,
thus reducing noise and visual impacts in the East Kempsey area.
Rest areas
Rest areas for both north and southbound traffic are proposed on the southern edge of Tamban State Forest.
The rest areas require minimal clearing of native vegetation and are situated away from sensitive land uses. They provide convenient opportunities for both light and heavy vehicles to stop and rest. The rest areas are located a suitable distance from other designated stopping areas.
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