2009
These photos show existing and imminent further collapse and erosion at Como
Beach. Last year the Council carried out some repairs. Much of this
work has been damaged again. The remaining older works have also been
seriously damaged. This of serious concern beyond the City of
South Perth, due to proximity to the freeway. The Kwinana freeway
arterial transport link is a vital part of WA's economy. Storm damage
here could stop car and train travel. The City of South Perth has been
able to fund minor works. This entire section of the Swan river needs
much more protective engineering and is beyond the City's ability to
provide funding. Click on the photos to
view them in full screen |
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| Preston Street wall
showing blocks with mortar failure and blocks about to be extracted by
the next storm wave event. |
Preston Street wall
showing blocks with very little remaining mortar, about to fail in the
next storm. |
Preston Street, more
blocks without much mortar left. When these blocks are plucked out by
waves the sand behind the wall will erode rapidly. |
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| Preston Street: The
wall in front of the public toilets collapsed forward when the front
concrete slab fell into the gaping space left by storm extraction of
supporting sand. |
Preston Street, a
better view, showing clearly how the wall collapsed forward onto open
space formed by wave removal of sand underneath the slab. |
Preston Street,
another view of the forward collapse. |
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| In front of the SP
Golf Club, showing rapid erosion towards the freeway. |
Erosion progressing
rapidly, now at the edge of the bike path, very near the freeway
boundary. See the truck behind. |
Palm trees, roots
undermined, collapse onto freeway imminent in the next strong westerly
wind. |
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| Blocks in an older wall,
without mortar, about to collapse. You can see straight through the gap. |
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2008
These photographs show that waves and ripples extract fine sandy
material from behind the protective limestone walls, drawing the grains
out the drain holes and spaces between blocks, allowing collapse. The
vertical walls are hit by the full energy of waves. There are
alternative wall designs that would allow energy dissipation and less
destruction. |
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Limestone blocks at the foundation of Comer Street bridge, showing
arched effect. The sand underneath has washed out, the blocks are
unsupported and about to collapse. Front blocks are falling backwards
into empty space. Bridge support pillar seen in left margin of photo. |
Empty space clearly visible beneath top layer of small blocks. Fine
sand has been washed out by wave action. |
Collapsed footpath at Preston Street
jetty. Water action has washed out the sand grains under the footpath
and the concrete slabs have collapsed. Simple backfill with normal soil
will allow this to happen repeatedly. Graded fill and/ or geofabric
could prevent this. |
Location photo, showing area of
footpath collapse, behind apparently intact front decorative limestone
wall. |
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| Foundation blocks at
Preston Street. A base block has been sucked forward by wave action,
leaving top blocks at the start of the jetty unsupported, ready to
fall. |
Foot of Preston St
jetty, showing extracted block and undercutting of the steps. The steps
are sitting directly on sand, without foundation, and are being undercut
by wave action. |
Jetty, extracted
block and undercutting, showing proximity to Preston Street footbridge
supports. |
Protective wall at
Comer Street bridge, showing bottom layer of blocks being sucked forward
by wave action. Wall collapse is imminent. |
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| Effect of wave
erosion at Comer Street. Erosion face is only eleven metres from freeway
boundary. Photo shows proximity to road and train. |
Como Beach view,
showing some protective effect of existing groynes. Note that sand
deposition pattern shows storm action from north-west, not south- west. |
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