River Surfing in Cairns?

Just after writing about how the mouth of Barr Creek can have violent episodes, I was able to actually able to film another creek having one.  Deep Creek at Clifton Beach is about one quarter the size of Barr Creek and longshore often blocks its mouth with sand during the dry season.  Last week the mouth of the creek was a mere trickle and then we had a little bit of rain.

The creek came up so fast that a little old lady who went for a walk along the beach could not get back.  I had helped her wade back across by walking out into the sea and crossing where the force of the water was less.

Some people arrived and were quite worried that their big dogs would jump in and get washed away but dogs have skinny legs and seem to be able to walk through really fast water so they relaxed.  Then everyone just started having fun.  A man was trying to body surf the waves but his dog kept climbing on his back and riding him like a surf board which was really annoying.  .

This time I could stand in right beside the channel and film the biggest of the waves just in front of me and I saw a lot of things that I had never seen before and you can see some of them in the video.  The standing waves move slowly upstream.  When they get really big, they collapse into rolling surge of slosh and which is washed downstream leaving the surface of fast flowing water almost flat.  After a few seconds, a new set of standing waves formed and over twenty seconds grew to full size and then as before collapsed.  I always thought that ocean swells moved through the flood and made the standing waves peak but this is not the case.  The standing waves were in this case a self-generating cycle.  In some of the standing waves, vortices are making patterns in the crests of the waves.

In my search for information about standing waves I discovered that if Barr Creek was in America, people would go nuts about it.  The Waimea River on the Hawaiian Island of Oahu is their version of Barr Creek

   

Does Barr Creek really compare to the Waimea River?  They are almost perfectly matched - look at this.

Barr Creek with 500 m scale bar (images Google Earth)

Waimea River in Oahu, Hawaii

The difference is that Barr Creek has a maximum drop to the sea of about 3.5 m whereas the Waimea River drops down by 6-7 m as the beach is built up high by 10 m waves (their king tides are only 0.5 m!).  Barr Creeks standing waves top out at about a 1.5 m high whereas the Waimea River standing waves seem to be twice as big at full power.  Like the Waimea River, one has to wait until the mouth is blocked and the creek fills up with freshwater and when it is on the point of bursting out.  Kids sometimes dig a channel on a very low tide and off it goes.  Unfortunately this is not a common event.  However Barr Creek has several tide powered events every year and where the water drops about a metre between the creek and the sea and there is still plenty of action.  These  events are bigger than my video of Deep Creek.  The best time to play is when the creek is running fresh during the wet season and you do not have to worry about box jelly fish but you always have to look for crocodiles.

How the Creek Ate the Beach

Strange combinations of normal events can synergise to do as much damage to the coast as cyclones.  As climate change kicks in and slight increases in sea level and slight intensifications of trade wind systems occur, these synergies become more significant as these events are likely to cause somewhat more damage and take somewhat longer for nature to repair.  In fact in recent years, most of the damage to the Queensland coastline in places that were not directly hit by cyclones, seems to be due to synergistic events.

A nice wide beach is just what you want on coming into the cyclone season

About 8 weeks later the beach was entirely gone leaving nearby houses highly exposed (23 Dec 2011)

Coming into the cyclone season, I was happy that the southern end of Holloways Beach had a 25 m wide crest that would provide an effective buffer against most cyclones.  A few weeks later this buffer had been entirely eaten away completely and trees were being undermined and some were falling into the sea.  The culprit was a combination of high tides and strong winds which is a regular and not very destructive occurrence, synergising with the meandering of the small tidal creek to create the most efficient beach erosion system I have ever seen. 

The eroding sand cliff was over 2 m high in most places 

In about 60 days, the mouth of Barr Creek moved by approximately 300 m and many thousands of tonnes of sand was removed from the beach.  In previous post I have covered how Barr Creek which is tiny tidal creek can become a serious geomorphological force when high tides combine with longshore drift.  In this post, I will describe how this same system became locked into a highly destructive cycle that resulted in the creek mouth rapidly migrating northward along the beach and eating away the protective foredune in the process.

Same position, looking in the opposite direction with the creek mouth in its normal state

Where Barr Creek crosses the beach, it meanders just like any other creek that flows through sandy ground.  Straight sections of creek begin to curve and curves grow more pronounced until they cut through the crest of the beach and new mouth forms.  Usually the meandering curves are restricted to the protected estuary side of the beach with the creek straightening just in time to pour into the sea.  Low swells and high chop often surge into the creek mouth on the incoming tide and dissipate their energy in the shallow waters over the sandbanks within the estuary.  As the sides of wave exposed creek mouth have a profile similar to the beach, the waves do little other than swash a few handfuls of sand from the beach into the creek channel and add a little more velocity to the inflowing tide.  This is the normal condition of Barr Creek. 

Sometimes the beach near the mouth is stable for long enough for beach vegetation and even trees to grow

Once every ten to fifteen years the creek has meandered to its maximum curvature and has created a high sand cliff that faces the ocean but which is protected from wave attack as the channel lies behind the beach crest.  High waves near the peak of a king tide can now wash right over the thin remaining beach crest that lies between the channel and the sea.  This delivers enormous amount of sand into creek channel resulting in continual narrowing of the channel at the same time as a king tide is trying to flood into the estuary. 

Washed over beach crest and narrowed channel, March 2015

The narrowed channel results in very fast currents that sweep away sand from the base of the bank on the landward side of the channel, creating a sand cliff.  The cliff retreats as unsupported sand falls into the channel and is also removed by the current.  At the same time, the washed over beach crest on the other side is being lowered and allowing waves to surge over the top, where they cross the creek and slam directly into the sand cliff.  Each time part of the cliff collapses; it is swept away by the extraordinarily strong currents in the channel.  The powerful wave and current attack on the sand cliff which faces the ocean is what eats the beach. 

Beach has just reached a critical state where waves can attack the outer bend (8 Aug 2011)

Creek is now locked into a northward migration (25 Sept 2011) - GoogleEarth Images

View of creek mouth on 24 Sept 2011 with kids playing in the current

Sand cliff or scarps also form on regular beaches during cyclones but they are usually much smaller being on 0.5 to 1 m high rather than the 2.5 m high sand cliff created where the channel has cut through the beach crest.  Also sand washed from the beach into the sea usually forms a protective offshore submerged sandbar that helps to reduce the level of wave attack on the beach.  In the case of Barr Creek sand eroded from the sand cliff helps to maintain the extreme currents that transport so much sand and this helps lock in the destructive cycle. 

Post Cyclone Larry (Cat 4) erosion scarp - the landfall was 100 km further south

Cyclone Larry seas were rough but not exceptional and the beach could easily endure

So far we have covered why the beach retreats so rapidly but we have not covered why the mouth of the creek moves along the beach at a high rate.  The whole process is driven by tidal currents moving sand.  Without the currents, the sand would just be swashed up and down the beach as it normally is and the beach would remain much the same.  When the mouth is migrating, longshore drift keeps delivering sand to the creek mouth forcing the creek mouth ever further to the north.  Outgoing tides passing through the narrowed, north pointing channel also deliver large amounts of sand to the creek mouth.  The result is long tapering sand spit that rapidly extends on the seaward side of the channel that constraint the channel to the base of the sand cliff.  In the next incoming tide vast amount of sand are swept over the sand spit into the channel forcing the channel back against the sand cliff repeating the process that eats the beach.  So the key element to the migration of the creek mouth is the rapid extension of the sand spit which is washed over at high tide.  The surprising thing is that the process is self-generating and can repeat for at least 30 days. 

When Barr Creek started to destroy mature beach trees, the council cut through the sand spit (23 Dec 2011)

The new mouth seen 6 months latter, however a 250 m long erosion scarp is still visible to the north

This geomorphological process converted a relatively safe beach into a highly exposed beach that could have enabled a cyclone to eat the whole beach reserve and threaten houses.  Events before my time may have been even more spectacular.  Long term residents say that the mouth of the creek was once a few hundred metres north of where it is now.  In a 1952 aerial photo, there is a hint of this being the case as the creek mouth seen in the photo has pushed more than 250 m north of its normal position.  Behind the current foredune is a freshwater lagoon which may have been created by the creek as locals say that the creek flowed behind the houses for a period. 

1952 Aerial photo showing the creek mouth eating the beach to the north

Behind the beach is a swale with a freshwater swamp full of Bullrush, the smooth patch in the above photo.

Another reason for understanding the behaviour of creek mouths is that they are often dredged to maintain channels for navigation or to provide sand for beach replenishment.  Currently the Moon River just north of Yorkeys Knob is being dredged and is causing terrible beach erosion in Half Moon Bay and now Richters Creek is being dredged to provide sand for replenishing Holloways Beach.  Each time the creek mouth is dredged, there is a massive impact on coastal processes in the vicinity of the creek mouth and I wonder if it these impacts are actually adding to the erosion of Holloways Beach in the long term.  These systems are complex and take years to respond to changed conditions so it would be easy to misinterpret action and response.

Most creek mouths are pretty stable and have been in the same position for as long as we have records.  Creeks like Barr Creek that have wandering mouths are comparatively rare.  Currently I know of only Barr Creek and Hartleys Creek at Wangetti Beach which are unstable and have mouths that regularly move by more than 100 m.  Larger creek mouths such as Richters Creek are also subject to similar processes.   As the watercourse becomes larger, the balance between the forces of tides and waves changes and it is probable that river mouths rarely migrate the way that smaller watercourses can.

Postscript

It took a few years for the beach to fully recover.  Whilst the face of the beach quickly recovers, there was a half metre deep hollow at rear of the beach as neither tides or wind penetrated to the rear of the beach to bring in sand.  Eventually, a combination of very high tides and rough weather resulted in waves that could swash right over the beach and into hollow.  As the swash drained back to Barr Creek along the hollow the water surged across the beach in one direction only and this quickly brought in enough sand to fill the hollow.  We have also recently had good sand supply from the Barron River and the beach has now grown tall enough to support large areas of beach creepers, something which I have not seen on the beach before.

Holloways Beach South in March 2016

The Secret Power of Ordinary Coastal Processes

For a long time geomorphologists (people who study how landscapes evolve) thought that is was mainly day to day coastal processes that shaped our coastline.  Then came a realisation that many coastal features were in fact created by major events from super cyclones to tsunamis.  Major events then became the main focus of study.  But there seems to be another agent of change that possibly has as much effect as major events and this is synergies of ordinary events.  In more than twenty years of observations of the Cairns Northern Beaches, these synergies have caused more beach erosion than several major cyclones. In this post and a future post, I will describe two synergies that can move vast amounts of sand in periods of hours.

One of most dynamic sections of coastline near Cairns is Barr Creek, which lies between Machans Beach and Holloways Beach.  This tiny little creek is only 1.2 km long, yet it can turn ordinary tides into dramatic events.  Barr Creek is unlike all of the other creeks in the region as it is an ancient abandoned mouth of the Barron River.  The other creeks have catchments on side the mountain ranges and their channels are maintained by flooding rains draining back to the sea.  Barr Creek barely has any catchment at all, just fringing mangrove swamps.  In theory, when turbid seawater fills into the Barr Creek at high tide, sediment should settle out of the still water and rapidly fill the creek in.  This is exactly what happened in the nearby Blind Barron, a mouth that was abandoned approximately 70 years ago.  Yet Barr Creek maintains itself.

The mouth of Barr Creek migrates from side to side

Most of Barr Creek can be seen from the beach

Barr Creek 1 km upstream is almost too small to turn a small boat

Barr Creek's secret is that it has flood-like outgoing tides.  No other creek in the region has these.  I suspect that on highest astronomical tides (~3.3 m), seawater expands over an almost flat ground surface in areas with mangroves and salt pan.  As tides get higher, the area that is flooded increases exponentially and the volume of water in the Barr Creek estuary would be much greater for an extreme high tide than a normal high tide.  When the tide turns, all of that extra water has to squeeze out of a creek mouth that is always being narrowed as longshore drift fills the mouth with sand at a rapid rate.  Longshore drift occurs when trade wind driven waves strike the beach at an angle and their swash pushes sand along the beach.  On the outgoing tide, waters flood out through the narrowed mouth at high speed creating standing waves that can be more than a metre high.  Ocean swells also force their way up into the outgoing flood and momentarily transform standing waves into raging peaks of water as they pass.  When conditions were like this we used to drop everything and go white water rafting (the video does not show a full power day).  After the flood has surged more than one hundred metres out to sea it plunges through a rolling wave than marks the end of the flood and the start of the sea.

Underneath the surface the outgoing flood is a turbulent maelstrom.  The sandy bottom is not smooth but a complex pattern of mega ripples and swirling vortexes that vacuum sand of the bottom and inject it into the flowing water.  A single tide can transport enough sand to create an alluvial fan that extends 100 m into the sea and which would require more than 2500 tonnes of sand by rough calculation.  A continually rolling wave is located at the seaward edge of the alluvial fan.  Inshore waters are shallow so the alluvial fan ends with a steep drop of only half a metre.

Strong longshore drift removes the alluvial fan within a few days to weeks.  The same longshore drift brings new sand to the creek mouth where it is sucked up the creek to form an alluvial fan that faces upstream.  Sand accumulated in the creek mouth in this way provides material for forming a fan in the sea when the tide runs out.

Aerial view showing both alluvial fans.  The fan in the sea is 85 m long and is mainly from one tide.

It is amazing how big the alluvial fans can get.  At the front-left are a few mega-ripples

Beaches often seem to be static places, adjusting only slowly to the balance between accretion and erosion, however the truth is that every wave moves more sand than a good man can shovel in a minute.  Usually the amount of sand added and removed is in balance.  It is only in special places where sand movements are not balanced that true level of movement is revealed.

Kids love the high banks where the creek cuts into the beach

Getting rolled along by the incoming tide is fun too!

There is a funny side to the Barr Creek tidal movements.  Years ago Holloways Beach had a pub and Machans did not.  So people would come across the creek at low tide then go home in the dark.  At night you can’t see power of the water or its depth.  Many people have been swept away attempting to cross the creek.  Lucky they could all swim.  The incoming tide is pretty nasty too and some people got swept up the creek into the mangroves and you can imagine the fun: drunk in the dark and staggering through the mangroves.

On a particularly violent day when outgoing tide was reinforced with a freshwater flood, I was out there having fun when a rescue helicopter came out and started circling around me.  I was trying to surf the standing waves on a competition surf ski which can be paddled to about 15 km/h.  But the water was much faster and I would paddle upstream like mad whilst getting sucked backward through the flood until I caught a standing wave and hopefully surfed.  Of course you can’t see what is coming when you are going backwards which makes it very exciting and it is almost impossible to go through the roller backwards without coming off.  Beyond the roller is flat calm sea so you just get back onto the surf ski, paddle to the beach and go again.  Of course the rescue helicopter shows up just at the point of wipe out and thinks I am in trouble and started preparing to rescue me, which was embarrassing.

Barr Creek mouth widened to 60 m after a cyclone when Barron River water flowed through fields into Barr Creek 

In this post I have talked about how a synergy of ordinary events can create very powerful forces.  In a future post, I will show the damage this process can do when it combines with other ordinary events to create an extra-ordinary synergy.

For more information on coastal processes, see the subject index

Beach Recovery at Yorkeys Knob

In the 1950's the sea was threatening to eat the houses on esplanade at Yorkeys Knob.  The original cause of this crisis took place in 1927, when the Barron River had carved a new channel through the cane fields to connect Thomatis Creek which flowed to the Barron with Richters Creek that went to the sea.  This new route was seven kilometres shorter than the old course of the Barron River.  Some years later, the mouth of the Barron also moved north by nearly 2 km after breaking through the beach during a flood.  Rivers pump sand out into the sea, yet only when the near shore waters near river mouths become almost choked with sand, do waves to return some of this sand to the beach.  It has taken nearly eighty years for the flow of sand back to the beach to be restored and beach to grow to its maximum width.

Changes in Yorkeys Knob Beach 1952-2015 (click here to enlarge)

Sand mining from the bed of the Barron River continued until the 1990's and intercepted both the 20 000 tonnes of sand coming down the river each year and consumed an additional 70 000 tonnes per annum of previously deposited bed load.  This consumption of the sand supply had a terrible effect on the beaches particularly Machans Beach and Holloways Beach, which lie between the old mouth of the Barron River and the new mouth at Richters Creek.  The fight to protect Holloways Beach and Machans Beach are covered in previous posts (see Coastal Protection in the subject index).  In contrast, Yorkeys Knob Beach is positioned to receive the high volume of sand that takes the shortcut to the new mouth and as soon as sand mining stopped began to grow quickly.

The growing width of Yorkeys Knob Beach provides more than a happy story of how a beach was saved, it is a chance to answer a swag of questions about how coastal features form as they have literally been forming in front our photographic eyes.  These questions are important to land management as well as being scientifically interesting.  Developers like to claim that dense coastal vegetation is just regrowth and that they should be able to remove some of it to create views.  Dense vegetation developing where previously there was open sea could affect the public by blocking cooling sea breezes and possibly by allowing increased mosquito activity.  Conversely, a wider beach with dense vegetation provides a much better buffer against storms.  Scientifically interesting aspects include the development of landscape features such as chenier ridges form and how and why some areas become impoverished grassland yet metres away a ferny rainforest is created.  Topics of scientific interest will be covered in future posts.

In overview, it appears that between 2002 and 2008, the beach got wider by approximately 5 metres  per year.  From 2008 to 2016, the position of the beach has been stable as sand is now able to escape around the rocks at the northern end of the beach.  Recently the beach has been getting higher rather than wider, with the foredune growing about one metre in height.  As the beach grew, a series of small ridges and swales were created that are now stabilised by dense grass and herb cover.  In places trees colonised, mostly in lines that were probably created by high tides washing seeds up onto the foredune.  Many of these seedlings have grown to become trees that are approaching maturity.  In places the dense wall of regenerating trees is lifting off the ground and an open understorey is developing where is breezy and open but shady.

2010 (left) and similar 2016 views (right).  The foredune has become much higher and has continuous vegetation

Another important observation is the resurgence of native plants.  In my first intensive survey of this area, much of the vegetation on the low dunes was composed of introduced species.  There was para grass, guinea grass, Tridax daisy, Hyptis, Singapore daisy, Chinese violets and Mossman River grass, which has nasty burrs that penetrate our skin.  Most of theses exotics have waned and been replaced by a vigorous sward of native grasses and herbs.  Healthy natural vegetation looks better than weed infested areas.  Native plants seem to fit together, each providing a different visual texture and each occupying a defined area.  In contrast exotic species tend to run rampant and form smothering tangled masses which 'lack natural design'.  The exotics are still present but have only a minor presence.  The photos below show how they were.

Top: Tridax daisy and Mossman River Grass (the nasty one)| Bottom: Singapore daisy and Hyptis

For me, seeing these changes is not a matter of good memory.  Since approximately 2004, I have been photographing a very wide range of subjects using geotagged photos.  I am possibly one of the leading practitioners in the world when it comes to using photos to track ecological change, yet after more than fifteen years of development, I am still working hard to make a system that makes it easy monitor the environment with photos.  If anybody thinks that they can do time series research without having developed or acquired powerful tools for this purpose, they will have a very hard time matching photos in future.  In another post I will describe how to use photos for monitoring.  Most of the hard work is done by a database application that I have been developing for many years.  The information in this post comes mainly from my personal photo collection, aerial imagery from Google Earth (thanks Google) and some really old aerial imagery that I have scanned in.  To make the beach fit better on the page. the aerial photography has been rotated.

Coverage of geotagged photos - you can never have enough

Finishing off the Machans Beach Seawall

After a few close calls with category 5 cyclones, a heavy duty rock wall is being constructed for protection.  Machans Beach seawall is reaching the final stages of construction and the causeway that was used by trucks to take rock out for placement on the wall is now itself being pulled up and placed on the wall to create a much thicker layer of rock armour.  As the causeway is about 2 km long, removing the causeway is a huge job. 

Causeway is located on left and is separated from rock wall by about 5 m

A pair of excavators are working together at the end of the causeway.  One fishes up rocks from the end of the causeway and places then on the side of the causeway between the excavators.  These rocks are then picked up by the second excavator and placed on the seawall.  Each stone is carefully placed and tamped down to ensure that it is unlikely to move.  It is a strange thing as the stability of seawalls increases when the amount of open space between the rocks increases, so tightly placing the stones possibly weakens the wall.  However people will climb over the wall so tightly placing stone improves public safety. 

Excavators passing stones from end of cause then on to rock wall

Tamping down a rock

At the top of the wall is a broad lip that is out of reach of the excavators removing the causeway and rock is placed on the lip directly by a smaller excavator equipped with a rock grab that lifts rock directly from a conveniently parked semi and places/drops the rocks onto the wall directly.  A white sheet of geo-fabric prevents soil from washing into the gaps between the rocks. 

Lifting rock from a semi and placing it on the seawall

The truck has to negotiate some tight spaces when delivering rock to the esplanade but with a bit of toing and froing, it gets around the corners.

A heavy responsibility, you can't damage the pub

Gradually sections of finished seawall are emerging. There is also a hidden part of the seawall, the base of the causeway will remain in place to provide support to the toe of the seawall.

Finished seawall

As the causeway was built over a small beach that ran along the base of the old seawall, the local sand supply to Holloways Beach may have been interrupted.  The southern part of the beach fared quite well as it is can receive sand from Barr Creek and from an off-shore sandbar that has migrated in but the northern part of Holloways Beach is again in trouble.  Fortunately, it seems that the sand supply is recovering and the coastline around the Barr Creek Mouth appears to have prograded by as much as 20 m.  It is hard to tell what contribution the seawall has as the beach also progrades due to floods pushing sand out of the creek and prevailing winds moving sand along the beach but these events have temporary effect and sand erodes away again.

Where the people are is new beach

See also:

• Fighting the sea with sand at Holloways Beach; and
• Constructing the Machans Beach seawall.

Fighting the Sea with Sand

Machans Beach holds back the sea with a wall of giant rocks but adjacent Holloways Beach relies on a barrier of sand.  Trouble with rock seawalls is that once you get them, the beach usually does not return as seawalls create conditions unfriendly to deposition of sand.  So at Holloways Beach, sand plays the leading role in the fight to protect the private and public space from the sea.  Holloways Beach is again at the point of needing more sand so this is a timely post.

San Remo Beach (north end of Holloways Beach) chewed up by trade winds, Dec 2014

Cyclones can damage the beach but this is fairly rare.  The basic cause of the recurring erosion is lack of sand supply due to previous sand mining activity in the Barron River and changes to the location of the the Barron River mouth, which resulted in sand being delivered to deep water instead of the beaches.  A combination of high spring tides and rough weather caused by persistent tradewinds can also do as much damage over several days as a typical cyclone and have caused most of the erosion this year.

Holloways Beach in 2009

Sand has been pumped from the Richters Creek Mouth at the far northern end of Holloways Beach to the southern end of the Beach at least twice in the thirty years I have been associated with this area.  A few years ago another method of moving sand was tried, trucking the sand along the beach.  As for the pro's and con's of trucking sand compared with pumping sand, I am not totally sure but here are my best guesses:

• Trucks run along the intertidal part of the beach so do not damage any private or public property whereas a pipeline that is installed for up to six months needs to be placed above the tidal zone.
• Trucks can place sand anywhere on the beach whereas pipelines are less flexible in this regard;
• If the sand is dirty, some of the dirt can be removed when the sand is loaded into truck whereas pumped sand includes the dirt (silt), however the silt is usually washed out at the receiving end leaving the beach clean but creating a turbidity plume in coastal waters which is undesirable; and
• In areas where the beach is narrow and the watertable is high, it might be difficult to get the pumped sand to stay on the beach rather than being washed into the sea by the stream of water that moves the sand.

The response of the operator was that trucking sand had been selected for environmental reasons.  In all approximately 14 000 cubic metres of sand were moved up to a distance of 2 km.

Truck hauling sand along the beach

End loader back blading the beach (dragging the blade) to flatten the beach for the trucks

Later in the afternoon, the tide came in and washed over the track

Initially the sand is dredged up by the same sort of dredge that would be used for sand pumping.  The sand is dropped into a bunded area which captures the silt-laden water running from the pumped sand.  Bunds are low earth or sand walls.  In this case, the bunded area was on a broad unvegetated part of the beach and much of the muddy pumped water was able to be filtered as it sank into the beach sand.  The area was also quite large so any sediment suspended in the water had time to settle once the water slowed down.
.

Dredge in mouth of Richters Creek

A small excavator would periodically heap the pumped sand into large heaps to allow the sand to drain and would also load the trucks.  The trucks were large articulated six wheel drives.  Despite looking like the ultimate all terrain vehicle, these trucks have one serious limitation.  They need a track that has very little crossfall and cannot drive along a beach that slopes at the normal angle. Their high centre of gravity and the fact that the back of the truck can rotate independently of the front creates means that the trucks could roll over relatively easily on sloping ground.  The slope of the beach was resolved by using an end loader to maintain a flat track near the high waterline.

Bunded area/sediment pond with excavator for retrieving sand from the end of the pipeline

Stockpile of gray sand - see colour of sand on adjacent beach

Sediment captured within bunded area, went hard with time and
the area was buried in sand when the site was cleaned up.

The new sand was coarse and gray having been stained by black organic material which is present below the surface of the underwater sand reserves.  The coarse gray sand was not very pleasant and a few months had to pass to give sun and sea time to rework the sand and return a  pleasant texture and colour.

So was the trucking of sand successful?  I think so.  The beach has maintained its position for six years.  Without the sand, it is likely that the seawall constructed to protect homes in Hibiscus Lane would have been exposed and wave action and currents would have changed to make Holloways Beach hostile to natural beach maintenance processes.

The downside of restoring Holloways Beach with sand was the removal of sand from the mouth of Richters Creek.  A large sand spit had formed a hundred metres out from the mouth and possibly was on the verge of becoming a vegetated sand ridge.  Removal of sand from the mouth of the creek lead to the collapse of this sand spit.  Only six years later is the spit beginning to reform.  Sometimes I wonder if the spit building up at the mouth of Richters Creek would have caused the Holloways Beach to prograde as the spit changed the shape of the coast.  As waves crash directly into the sand spit there is no long shore drift and this area of beach becomes a natural sand trap.

The sand spit that was lost due to the dredging, Holloways Beach in background