Windy Point Coastal Erosion Management Work from 22/02/2021

From 22nd February 2021, heavy machinery will be operating on Lagoon Beach in the area between Windy Point and the southernmost load line opposite the Environmental Tours boatshed.  The machinery will be carrying out erosion management work to the sand dunes at Windy Point.

It may be necessary to limit public access to some sections of Lagoon Beach during periods of machinery operation.

The work is expected to take up to 50 days to complete, however this time may be extended or reduced.  Updates on timing will be provided via Householder as the work progresses.  Further information is provided below and in the attached Questions and Answers sheet.

Background

Erosion has been affecting Lagoon Beach at Windy Point for many years.  The problem is now quite severe and if not addressed soon, erosion will threaten Lagoon Road, the high voltage electrical cable and other built infrastructure.  Erosion results in the loss of coastal vegetation and loss of habitat for nesting seabirds.  The Lord Howe Island Board (LHIB) is implementing a “beach nourishment” program to restore the dune at Windy Point in order to manage the erosion, protect infrastructure and protect the dune environment.

Description of work

Beach nourishment (also known as beach scraping) is a technique where sand is moved from areas of the beach where there is natural sand accumulation, to the areas where there is erosion.  It is in effect a “reversal” of the natural erosion process.  The LHIB has engaged All Island Service as a contractor to carry out this work.  The contractor will use the LHIB excavator and rough terrain dump truck to scrape sand from the northern section of the beach, between the access track opposite Bowker Avenue and the southernmost load line opposite the Environmental Tours boatshed.  The sand will be trucked down Lagoon Beach to Windy Point where it will be deposited into the erosion area.  At times, an additional excavator and truck may be used to speed up the work.

As part of this work, the geotextile sandbag wall at Windy Point will be dismantled and removed.  Additional sand will be placed into the area where the sandbags are removed.

The target for the work is to transport between 7,000 and 10,000 cubic metres of sand.

As sand is deposited, some will be washed away by waves and currents.  The contractor will be working to deposit sand faster than the natural processes which remove it.  This will create a net build-up of new sand, and will ultimately restore the dune and beach to a more stable profile. 

The natural rate of sand removal can vary widely, and this will affect the amount of time it takes to complete the work.  This has been taken into account in our planning, and may cause the timeline to be extended or reduced.

The work is being undertaken now because of the pressing need to minimise further erosion, and to ensure completion well ahead of the winter months when stormy weather and stronger erosion forces are more likely.

 

Changes to beach access

The LHIB will endeavour to keep the beach open during the work, however there may be times when it is necessary to close sections of the beach to ensure public safety.  This will be indicated by signs, barriers and tape at beach access points.  Beach closures will only occur occasionally, and will only affect a limited area.  The LHIB will not be providing further specific notice of closures.

If you are using the beach while machinery is operating, please take care to:

  • keep out of areas which are closed;
  • stay well clear of all machinery;
  • supervise children and dogs;
  • follow the directions of LHIB contractors and staff, and move away if you are asked to do so.

The contractor will have safety watch personnel on the beach to ensure that people keep clear of operating machinery.

There may be times when you would like to access a closed section of beach, such as to move boats/kayaks/boards into the water from a storage area or to access a moored boat.  On these occasions, please make contact with the safety watch person on the beach before you enter the closed area.  The safety watch person will ensure that you can move safely past operating machinery.

Note that beach closures will only be in place while work is underway.  Once operations have finished for the day, the beach will be open again.

Where there is potential for beach events (such as Nippers) to be affected by the work, the LHIB will work with event organisers to minimise disruption and to ensure that there are no safety risks.

Impacts on beachgoers

  • Machinery will be operating on Lagoon Beach between Windy Point and the designated source area (up as far as the southernmost load line opposite the Environmental Tours boatshed).
  • Excavators and trucks will be visible on the beach and the foreshore.
  • There will be noise from machinery.

Work will usually be programmed in 6 to 8 hours shifts centred around low tide times.  On some days, work will take place over most of the day. On other days, there may be 1 to 2 shifts in the morning and afternoon.  Where possible, work will continue 7 days per week.

The LHIB acknowledges that there will be disturbance to the access and amenity of the beach.  Thank you for your cooperation while we undertake this important coastal protection work.

The Lord Howe Island Tide Tables are available at

http://www.bom.gov.au/ntc/IDO59001/IDO59001_2021_NSW_TP003.pdf

Further information

The attached Questions and Answers sheet provides additional background information on the beach nourishment work.  For further information, please contact David Waterhouse, Manager Infrastructure and Engineering Services on 02 6563 2066 or email administration@lhib.nsw.gov.au

Peter Adams

CHIEF EXECUTIVE OFFICER

Date: 15 February 2021

 

Windy Point Coastal Erosion Management Work

Questions and Answers

Is a permit required?

Yes. The work is being conducted under a Marine Parks NSW permit.

Will the work affect nesting birds?

No.  The sand will be sourced from areas of beach which are not colonised by nesting seabirds.  Where sand is deposited, and in the area where the sand bags are to be removed, care will be taken to ensure burrows are not disturbed.

Who is advising the Lord Howe Island Board?

Coastal engineers from the Water, Floodplain and Coast section of the NSW Department of Planning, Industry and Environment (DPIE) have assessed the erosion problem and have worked with the Lord Howe Island Board and Marine Parks NSW to come up with this approach.  In selecting this course of action, the DPIE engineers conducted a site inspection, assessed logistical and engineering challenges and also considered historical data on coastal changes and previous erosion protection work.

How much will it cost and how is it being funded?

The program has received $715,000 from the Water, Floodplain and Coast section of the NSW Department of Planning, Industry and Environment.  This amount has funded the 2020 purchase of the new Hydrema rough terrain dump truck and will fund labour, materials, survey and monitoring work for the program.  The Hydrema will provide an ongoing capability for the LHIB to manage beach erosion.

Will it cause loss of sand at the northern end?

The work will source sand from the section of Lagoon Beach between the access track opposite Bowker Avenue and the southernmost load line opposite the Environmental Tours boatshed.  This area of beach accumulates sand through ocean currents in the Lagoon.  It is planned to remove a layer of sand up to 60cm deep from the beach and transport it to the Windy Point to fill the erosion scour.  Waves and currents will deposit more sand onto the beach at the source area, so that after a few days or weeks, the beach profile will be similar to its original state.  So while there will be a short term reduction in the amount of sand on the northern part of the beach, the beach will soon be back to normal.  The Board has regularly sourced sand from the beach north of Windy Point to conduct emergency erosion protection, and experience has shown that the source area returns to its normal profile within a few days.

Will this be a permanent solution?

Filling in the erosion at Windy Point will create a more stable beach profile which is less prone to further erosion.  Removing the sandbag wall will also reduce the rate of erosion either side of the current wall.  However Lagoon Beach is a dynamic environment and there will always be movement of sand.  We expect that the area will continue to require regular top up maintenance, but the amount of sand required will be considerably less than the amount we are moving now.  NSW DPIE coastal engineers have successfully applied this approach to manage erosion on NSW mainland beaches, so there is a good indication that this will be a successful approach at Windy Point.  While considered unlikely, it is possible that the deposited sand will be rapidly removed again by erosion.  If this occurs, the approach will need to be reconsidered.

Why is the sandbag wall being dismantled?

The sandbag wall was put in place as a temporary protection measure to slow the erosion which threatened the Pinetrees Boatshed.  The wall provided good protection but is now reaching the end of its useful life.  It has also caused accelerated erosion on either side of the wall.  This “end effect” erosion would continue if the wall were left in place, so it needs to be removed.  Beach nourishment will place additional sand in the area where the sandbag wall is removed to restore the dune to a more gradual slope.

Why not extend the rock wall or sandbag wall?

Seawalls have both advantages and disadvantages as effective means of coastal protection.  At Windy Point, the most severe erosion has occurred at the ends of the rock and sandbag walls.  This “end effect” is the result of wave energy being deflected and concentrated at the ends of the walls.  Extending the seawalls on Lagoon Beach is very likely to move the erosion problem to the end of the new walls, rather than eliminating the erosion altogether.  Seawalls are also costly to build, and result in lasting changes to the landscape and the sand dune environment.

Beach nourishment also has advantages and disadvantages, but on balance it has been selected as the most appropriate method for managing erosion at Windy Point.

How will the beach be monitored?

The beach will be monitored by conducting aerial 3-dimensional photographic surveys.  A team from Southern Cross University will be carrying out surveys using a drone at completion of the beach nourishment, and then at 3, 6, 9, and 12 months post-completion.  This monitoring will provide valuable quantitative data on the erosion process and the movement of sand on Lagoon Beach.  This will assist the LHIB in evaluating the success of the beach nourishment and planning for top up maintenance.  It will also provide important information for long term erosion risk assessment and planning.

What will the future top up maintenance involve?

Top up maintenance will follow the same method as this work program, with heavy machinery being used to move sand from the northern section of Lagoon Beach to erosion areas at Windy Point.  It is hoped that once the dune has reached a more stable profile, the need for top up maintenance will become less frequent – but at this stage it is too early to estimate the requirements for future maintenance.

Will there be any impact on boats or craft stored in the dunes along the beach?

No.  Sand will only be scraped from the beach and will not be sourced from the grassy/vegetated areas of the dunes.  If boats or craft are left on the sand, they will be moved further up the dune away from the machinery operations.