CockburnCoast - Western Australian Planning Commission

CockburnCoast
Table 6.2: Reclamation, beach renourishment and dune creation within the
Cockburn coast district structure plan project area
Location Works Year(s)
Volume
(10 3 m 3 )
Scott Street to Dune 1984 - Dunes created, brushed ~31.8
Island Street construction 1986? and vegetated to restrict
(or Catherine
sand movement on to
Point?)
roads, car parks and the
railway, with groyne
maintenance prior to the
America's Cup.
Scott Street to Nourishment 1996 Land extended 60 m
~120
Island Street and dune
westward into water.
construction
With dune creation
behind. As part of South
Beach redevelopment.
Duoro Street to Nourishment 1964 - During three stages of ~61.2
Island Street 1965 South Beach restoration,
nourishment undertaken
in combination with the
construction of the Island
St groyne.
South of Temporary 2001
Catherine nourishment
Point
Note: * Outside the district structure plan study area
Associated works
There was localised
raising (1.5 m) of dunes
south of Catherine Point
in March 2001 due to
sand storage from
construction works.
Assumed to be removed.
Table 6.3: Historic structures within Owen Anchorage which are no longer functional
Location Works Year(s)
Removal
year
Bradford Tipped pre-1954 Superseded
Kendall limestone by onshore
seawall and
sediment
jetties
supply
Robb Rd Barge and ~1966 - Lost
boat wrecks 1971 function
~1987 - 90
Robb Rd Jetty 1892, ext. ~1972 -
in 1910, 1975
1943-44,
lowered in
1947
Omeo Boat wreck 1894 Early
wreck* 1960s.
Lost
function
Note: * Outside the district structure plan study area
Why constructed?
Bradford Kendall (now
known as ANI Bradken)
Foundry was established
on high ground adjacent
to beach. Tipped
limestone wall to prevent
further damage to the
property.
Barge and boat wreck
that behaved as a semidetached
breakwater,
sustaining sand to the
north and reducing
supply to the south.
Constructed to unload
munitions and stock for
the abattoir. Contained a
stormwater drain.
Remnant jetty piles still
remain.
Barque wreck that
behaved as a semidetached
breakwater,
forming a tombolo and
sustaining sand to the
north.
Historically, the study area as a whole has experienced net
accretion (accumulation of sediment), with periods of strong local
erosion. The main source of material contributing to the net
accretion is the landward propagation from Success Bank, feeding
the Catherine Point salient. It has been suggested that this supply
has been artificially enhanced through the onshore transport of
dredge material disposed of during early excavations of Success
Channel. The structure of Cockburn coast is, in effect, two linear
sections meeting at Catherine Point. From here, the coast runs north
and south-south-east. This change in orientation, combined with the
wave climate, suggests a separation in the direction of net sediment
transport. Alongshore movement away from this zone in both
directions has been indicated by wave and sediment transport
modelling (MRA 2005b). Finer sediment cells are located within
these two larger sediment cells. The sediment cells are constrained
between fixed structures with varied levels of sediment bypassing.
For the coast north of Catherine Point, northwards transport over
summer and autumn generally exceeds the southerly reversal
during winter. South of Catherine Point, the angle of the shore
enhances southward transport and reduces the effect of sea breeze
wind waves, causing a net southwards sediment transport. These
basic patterns of movement have been complicated by the
construction of groynes in both sections of coast.
Further modifications to the coastline have the potential to
significantly alter the sediment budget and the behaviour of the
shoreline. The net sediment budget could be altered by
modifications to structures, beach nourishment programs and the
reduction/increase in onshore sediment supply from Success Bank
due to climate change.
district structure plan
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