By Chris Morris on Thu, 5 Jan 2012
News: Dunedin | DCC

By David Loughrey on Sat, 1 Oct 2011

Dunedin's battle of dunes

Otago Daily Times
Sat, 1 May 2010

Dunedin's Ocean Beach Domain is the frontline in an ongoing battle between sea and land that has serious implications for the low-lying suburbs behind the dunes. The forces at work, not least the hand of man, have shaped a significantly modified environment.

Change has been brought about by the pressure for raw resources in a developing city, the introduction of marram grass and ultimately the need to tame the coast for the physical protection of the city.

There are lessons here for those who are prepared to look at the mistakes of the past, say Paul Pope, of the Dunedin Amenities Society, and the late John Perry.

• Kaituna
Ocean Beach is a highly modified environment. The normal activity and movement of sand has been altered in favour of a more stable landscape. The former back-dune areas have been extensively mined and become recreation areas.

The coastline still stretches from the St Clair cliffs in the west to Lawyers Head in the east, but the sand dunes have become much thinner and steeper.

In 1848 in the west around St Clair, the sand hills were much smaller and lower, and the mouth of a lagoon ran through these dunes. They accumulated and grew as you moved east towards Lawyers Head.

High ground was in the west at the St Clair hills and in the east at the beginning of Otago Peninsula and beyond them, Otago Harbour and its extended tidal areas.

Between these features was a low-lying wetland named Kaituna. It was covered with silver tussock, rushes and flax and was an area of traditional food-gathering for Maori who sought tuna (eel), pukeko and weka.

There is also evidence that the Kaituna area was once thick with trees, probably kahikatea. They lay buried under the surface of the wetland and were often dug up and used as firewood by early settlers.

A significant feature was a track along the landward edge of the sand hills, which provided easy access to Kaituna.

By 1876 the urban growth of Dunedin had pushed housing to the edge of the sand hills at Ocean Beach. Sand was being removed constantly by householders to raise the level of their sections. Occasional floods are reported in the 1870s, but mostly from the harbour, into South Dunedin.

On one occasion a Mrs Rae and her two daughters were rescued by a gasworks boat crew from Rankeilor St. Their dog was reportedly left behind.

ODT Sat, 1 May 2010 by

Dunedin's Ocean Beach Domain is the frontline in an ongoing battle between sea and land that has serious implications for the low-lying suburbs behind the dunes. The forces at work, not least the hand of man, have shaped a significantly modified environment.

Change has been brought about by the pressure for raw resources in a developing city, the introduction of marram grass and ultimately the need to tame the coast for the physical protection of the city.

There are lessons here for those who are prepared to look at the mistakes of the past, say Paul Pope, of the Dunedin Amenities Society, and the late John Perry.

• Kaituna
Ocean Beach is a highly modified environment. The normal activity and movement of sand has been altered in favour of a more stable landscape. The former back-dune areas have been extensively mined and become recreation areas.

The coastline still stretches from the St Clair cliffs in the west to Lawyers Head in the east, but the sand dunes have become much thinner and steeper.

In 1848 in the west around St Clair, the sand hills were much smaller and lower, and the mouth of a lagoon ran through these dunes. They accumulated and grew as you moved east towards Lawyers Head.

High ground was in the west at the St Clair hills and in the east at the beginning of Otago Peninsula and beyond them, Otago Harbour and its extended tidal areas.

Between these features was a low-lying wetland named Kaituna. It was covered with silver tussock, rushes and flax and was an area of traditional food-gathering for Maori who sought tuna (eel), pukeko and weka.

There is also evidence that the Kaituna area was once thick with trees, probably kahikatea. They lay buried under the surface of the wetland and were often dug up and used as firewood by early settlers.

A significant feature was a track along the landward edge of the sand hills, which provided easy access to Kaituna.

By 1876 the urban growth of Dunedin had pushed housing to the edge of the sand hills at Ocean Beach. Sand was being removed constantly by householders to raise the level of their sections. Occasional floods are reported in the 1870s, but mostly from the harbour, into South Dunedin.

On one occasion a Mrs Rae and her two daughters were rescued by a gasworks boat crew from Rankeilor St. Their dog was reportedly left behind.

Consulting engineer Dave Tucker yesterday said engineering solutions were available to deal with the issue, while Sustainable Dunedin co-chairman Phillip Cole, also an engineer, said a retreat from the area was inevitable.

A report released on Monday identified South Dunedin, St Kilda and St Clair as "hot spots" vulnerable to what could be a 1.6m rise in sea levels by 2090.

The report on the effects of climate change in Dunedin was commissioned by the Dunedin City Council, written by University of Otago Emeritus Professor of Geography Blair Fitzharris and released on Monday.

It said the city would eventually have to protect, retreat or evacuate areas including South Dunedin, St Kilda and St Clair.

Other problem areas were the harbourside, the lower Taieri Plain, including the Dunedin airport, populated estuaries along the coast, and the ecosystems of upland conservation regions.

In his report, Prof Fitzharris said the city needed to focus on "adaptation" to deal with the problem, and that was not a one-off event but a process that involved awareness-raising, the development of knowledge and data, and risk assessment.

Some adaptation was occurring on a limited basis, he said.

"However, there remain significant challenges to achieving concrete actions that reduce risks."

Implementing measures such as planned retreat and dune management, building design, prohibition of new structures and siting requirements that accounted for sea-level rise was difficult.

Mr Tucker has previously told the council it needed to form long-term mitigation strategies to deal with the effects of climate change.

Yesterday, he said two areas of Dunedin were not protected by hills: the St Clair and St Kilda beaches area, and the lower harbour near Port Chalmers.

The areas of risk if the sea came through were not just South Dunedin, but all the reclaimed land in the city, including land up to the Dunedin railway station, and up to parts of the University of Otago.

He suggested a "barrage" across the harbour that would take advantage of a natural bottleneck between Port Chalmers and Portobello.

The barrage would link Goat and Quarantine Islands, trapping water in the upper harbour during high tide and releasing it at low tide. That would deal with sea-level rise at the harbour end of the city, and could include turbines to produce electricity.

The beach end of the city "could be saved in some engineering manner".

"You only need to go to Holland," he said, where technology had been developed to keep the North Sea out of the country.

"I'm quite sure if you got consultants from Holland they would come up with ideas to stop sea ingress."

Nature's way may be Middle Beach answer

ODT Thu, 27 Aug 2009

Pictures and stories last month serve as a timely reminder to those who will decide the fate of Middle Beach when the project team discusses the initial results from the year-long gathering of data in September.

In an Otago Daily Times front-page report six months ago, the Dunedin City Council reiterated that it would be looking at a range of "hard" and "soft" options for Middle Beach and that it would not be ruling anything in or out in coming to a solution.

The different types of solutions will have their own sets of unique problems and financial costs, a fact acknowledged by the council. The time scale of several years before any construction can take place, however, is the most telling feature of all.

So where does that leave the Middle Beach problem? The stadium costs and other major project spends will leave the council with very little money for this project.

The council has stated that $400,000 over the next three years has been set aside to deal with the problems (already depleted by at least $60,000 due to the recent events) but, rather alarmingly, no money has been set aside for a long-term management plan, or indeed for the four years until "any construction can take place".

By default, then, the council may have to consider the option that wasn't mentioned in either story but was raised at the submissions hearing - that of a "managed retreat".

• Often, the initial response to shoreline erosion is to build a sea wall.
• A sea wall will not solve the problem at Middle Beach.
• Sea walls force waves back to the ocean.
• These waves take the sand in front of the sea wall and deposit it far away from land.
• The water in front of the sea wall gets deeper and makes for bigger waves next to the shoreline, so you always have to build larger sea walls.
• The sea will always win this battle, because the force of water will always be stronger than any sea wall.
• Adopting a managed retreat policy at Middle Beach will be successful if it begins at a grassroots level.

An open and honest approach will have a successful outcome, as it will involve all major players in the planning process and address their concerns.

Although the process will take time, a consensus can be reached that will enable a managed retreat to be the best alternative to solving the long-term problems of Middle Beach.

Indeed, this could take place in the "several years" before any construction takes place, as quoted in the newspaper report.

One could argue that consultation at a local level could have already begun since the submission hearings in April 2008 to hear and consider the views of the people that will ultimately be affected by whatever action the council decides upon.

A golden opportunity presents itself to the council here.

An integrated planning strategy can be developed where people affected by the erosion can be relocated into new sustainable housing developments where they would no longer be affected by the current sewage, drainage and flooding problems that will continually arise whenever there is a downpour in South Dunedin.

Property owners who would be affected could have compensation paid at market rates for their properties, or "swap" their current homes for new ones built to replace them.

Managed retreat, in the case of Middle Beach, is an important soft engineering coastal defence technique which aims to achieve sustainable flood defence by creating new defences further inland and allowing the land behind the existing sand dunes to be flooded by the incoming tide.

The existing coastal defence, in this case the sand dunes, would be breached, allowing the land to be tidally inundated and colonised over time by salt marsh vegetation. When established, the vegetation disperses wave energy during storms, reduces erosion rates and provides an important habitat for coastal flora and fauna. A new embankment is usually constructed beforehand on the landward side of the site to reduce the risk of flooding.

It is widely recognised that managed retreat of a shoreline can reduce the costs of coastal defence while offering numerous environmental benefits. Managed or "planned" retreat allows the shoreline to advance inward unimpeded. As the shore erodes, buildings and other infrastructure are either demolished or relocated inland. In many situations attempting to stop erosion through structural or non-structural solutions is a losing battle.

Shoreline protection efforts and/or their repeated maintenance would be too costly and ultimately ineffective at preventing further erosion. A managed retreat approach typically involves establishing thresholds to trigger demolition or relocation of structures threatened by erosion. The advantage of a managed retreat system is that it is usually less expensive than costly structural stabilisation projects that may only be a temporary solution, especially in highly erosive areas such as Middle Beach. It also maintains natural shoreline dynamics and enables shoreline habitats to migrate inland.

There are no direct costs, aside from the removal of any defences already in place, and maintenance costs are very low. The inter-tidal region is able to dissipate wave energy and protect property and land, while supporting a wide variety of plants, invertebrates, molluscs, birds and fish. Sediment flow is also restored to its natural state; beaches can be naturally replenished due to erosion of the coast, providing protection and the balance of the coastline returns.

Yes, this method can be politically difficult to implement, particularly where significant development has already occurred. It may cause shorefront property values to fall. With an in-built political and institutional preference for "hard" engineering schemes this solution will face a lot of opposition.

But what came first - the shoreline or the buildings? The future, as we all know, is unknown. Scientists forecast sea level rises, but there are unknowns that could rapidly change their forecasts. Therefore, the traditional approach to design cannot be applied to Middle Beach, simply because historical data is less applicable.

A change in outlook is required by how people plan for such challenges, how the community accepts the change, and crucially, how our council involves the communities to adapt to change. Rising sea levels do not come into the equation, as most of South Dunedin is currently below the present sea level.

The council has an opportunity here to be both forward-looking and bold in its search for a solution to the problem. History has shown that man cannot control nature, especially where sea action is concerned and the council should take this on board when looking for a solution.

As the council parks and reserves team leader Martin Thompson said (ODT, 16.01.2009): "We are at the mercy of the sea, basically, in terms of what sort of storm events we get . . ."

A sobering thought indeed.

From a POLL at the Otago Daily Times Sat, 25 Jul 2009
Below are two comments related to the POLL

Channel 9 news - July 24, 2009 - 7:41pm

Council Contractors have been working to minimise the effect of erosion on Middle Beach which has occurred because of high tides over the past few days.

Local sports fields at Hancock park are in danger of becoming part of the coastline after the exceptionally high tides and winter swells have undermined sand dunes.

On Wednesday, this pile of rubble was sitting at the base of the dunes, but that pile has been brought forward to create a shock absorber to the force of the waves.

These developments are seen as a temporary measure, as the Council is currently gathering data in order to come up with a long term solution to erosion in the area from St. Clair to St. Kilda beaches.

Channel 9 News - July 21, 2009 - 7:16pm

Work is currently underway on Middle beach between St Kilda and St Clair, as erosion is threatening to undermine the sand dunes keeping the sea at bay from South Dunedin.

The issue has been a significant one for the city over the last few years, and is adding pressure to the Dunedin City Council to come up with a long term strategic plan to combat it.

Otago Daily Times
By Chris Morris on Wed, 15 Jul 2009
Eleven of Dunedin's coastal reserves look set to be given new protected status, at the expense of some recreational rights, in an effort to protect vulnerable sand dune systems.

The move would see coastal reserves next to beaches at Long Beach, Ocean View, Warrington and Karitane, and seven other locations, reclassified.Under the Reserves Act 1977, local authorities were required to classify the primary use of the reserves they owned.However, councillors at yesterday's community development committee meeting voted to approve the reclassification of 11 coastal reserves around the city from recreational areas to "local purpose (coastal protection)" zones.

Subject to final approval at the next full council meeting in August, the changes would become part of the council's draft Coastal Dune Reserves Management Plan, due to be released for public consultation in October.The new plan laid out the future rules governing work to protect dunes at Dunedin beaches.

To be protected

• Kuri Beach (two areas on coastal side of Taieri Mouth Rd)
• Brighton (coastal side of Brighton Rd)
• Ocean View (coastal side of Brighton Rd)
• Island Park
• Ocean Grove (coastal side of Tomahawk)
• Te Rauone
• Long Beach
• Warrington
• Karitane
• Waikouaiti (in the vicinity of Matanaka Dr)

Otago Daily Times
By David Loughrey on Mon, 21 Apr 2008
Accepting the eventual inundation of Kettle Park and a "managed retreat'' from properties in the St Kilda area are two of the more controversial methods suggested to deal with the erosion of Dunedin's beaches.

Those, and the views of 49 others, will form the basis of a Dunedin City Council hearing during the next three days into an issue that has attracted strong interest among beach users and the wider public.

The hearing is a response to investigations into stabilising the beaches, made more urgent last year when large portions of the sandhills were washed away during a stormy winter, leaving a perilously thin strip protecting Kettle Park.

Otago Daily Times
By Chris Morris on Tue, 17 Mar 2009

The Dunedin City Council has applied for retrospective resource consent to avoid any possibility of a legal entanglement over emergency beach repair work at St Clair and Middle beaches almost two years ago.

The consents, lodged with the Dunedin City Council and Otago Regional Council, were for a series of projects undertaken following storms in 2007, which caused severe erosion and threatened parts of Kettle Park.

The consents covered the transportation of rocks and sand to the eroded areas, the construction of rock "reno mattresses" to protect the beaches and dunes, and the removal of clay from the area for safety reasons.

The consents also allowed for more work to be undertaken should a repeat of the erosion occur this winter.

Yesterday, council parks and reserves team leader Martin Thompson said the five-year consents would cover the time it was expected to take to finish new beach management plans for the area.

From the Otago Daily Times website
The Dunedin City Council says it is looking at all options as it plans the defence of the city's most popular beaches from erosion caused by pounding Pacific waves. Study of the shape of sands to come A multimillion-dollar extension of the St Clair seawall as far as Lawyers Head, to protect St Kilda and Middle beaches, is among extreme "hard options" council staff say cannot be ruled out, while a host of "soft solutions" each come with their own problems. Council parks and reserves team leader Martin Thompson said yesterday a series of projects aimed at gathering data about the state of the three beaches was either finished, nearing completion or soon to start.
The work began in the months after a dramatic series of storms in 2007 caused significant erosion in the area - repeated when the storms returned last year - and threatened to send parts of Kettle Park crumbling into the sea. The projects launched in response included the work of two University of Otago students, who were conducting a monthly GPS survey, mapping the form and volume of sand on the beaches and how it changed over time. Also planned to start soon was a survey using ground-penetrating radar to locate the edges of the old landfill under Kettle Park, parts of which had been exposed by the severe storms in 2007, Mr Thompson said. The projects tied in with work already completed, including mapping the seafloor offshore from the beaches, ongoing monitoring of rip tides - which influenced erosion "hotspots" - and weather information from automated cameras at St Clair. Mr Thompson said the data would then be used in hydrodynamic computer modelling, mapping the impact of possible solutions - from a seawall extension to simply restocking the area with sand - on the beaches over a 50-year period. Other measures to be modelled included the construction of an offshore artificial reef, to dissipate the power of waves, he said. The modelling was expected to begin once the council established a new project team to co-ordinate the next stages of the work, possibly as soon as June this year, he said.
However, it could take the best part of a year to identify the preferred solutions and prepare a draft report recommending the best options to councillors, he said. The initiatives would then be presented for public consultation, and possibly become the subject of a resource consent hearing, meaning any construction could be several years away, he said. The data collection and modelling work had a budget of $335,000 for this year, but some of the possible solutions could be "quite expensive". Extending the St Clair seawall - considered an unlikely example, but one that could not be ruled out - was likely to cost "tens of millions of dollars" and raise significant aesthetic questions, he warned. "That would be a huge cost and maybe quite a structurally intrusive solution." Smaller "soft solutions", such as continually re-stocking the beaches with dredged sand, would be cheaper and less intrusive, but might mean "sacrificing" some vulnerable parts of the coastline to the sea, he said.

It was too soon to say what the likely measures taken would be, or what the exact cost could rise to. "We are not ruling anything out and we are not ruling anything in."In the meantime, the council had an annual budget of $400,000 to maintain a "holding pattern" of remedial work in the area, but the beaches remained vulnerable to further erosion in another series of big storms, he said. "We are at the mercy of the sea, basically, in terms of what sort of storm events we get . . . "If we get a run of storms again this year, we could be back in a situation where we are getting a lot of erosion."

Otago Daily Times
By Chris Morris on Fri, 16 Jan 2009
Large volumes of sand may have returned to Dunedin's most popular beaches, but the picture being painted by two University of Otago students may soon show if it is here to stay.

The pair, Teresa Konlechner and Charlotte Kidd, are engaged in a GPS survey of St Clair, St Kilda and Middle beaches, which aims to build a three-dimensional digital model showing the shape of sand deposits on the beaches.

The work is the latest in a series of monthly surveys undertaken by students, contracted to the Dunedin City Council, since last year's severe storms caused more erosion problems, stripping sand from the area.

And it's surprisingly tough work - the students cover up to 22km each day while taking up to 4000 measurements in the hot sun, and have survived close encounters with curious locals including, earlier this week, an angry sea lion and her young pup.read the rest of the article here

Dunedin beaches seriously eroded

Dunedin City Council parks and reserves team leader Martin Thompson said there had been significant loss of sand and some localised erosion, which had exposed the sand sausages to the east of the wooden groyne.

‘‘Work to recover these will be carried out over the next few days, along with the transportation of dredged sand to replenish the stockpile at the eastern end of the beach,'' he said.

The top of the ‘‘reno mattress'', which was installed near Moana Rua Rd in July 2007, had also been exposed. However, no significant erosion had occurred at this stage.

Since last June, the council had spent nearly $1.2 million on repairing and controlling the erosion, and about 30,000 cubic metres of sand had been moved or replaced in the area.

.. For The Future Of The City's Main Beaches
source link
April 21, 2008 - 5:34pm

Solutions ranging from a solid rock wall to an artificial surf reef are being considered by the Dunedin City Council, as it plans for the future of the city's main beaches.
Hearings on stabilising St Kilda, St Clair and Middle Beaches began today, with more than 30 people and groups asking to speak to the hearings panel.
Erosion of the beaches became a hot topic last year, when large portions of the sand-hills were washed away in Winter storms, leaving a sheer cliff between rugby fields at Kettle Park and Middle Beach below.
The beaches were put in more danger, after someone vandalised emergency measures put in place to protect the sand-hills.
The Council hearings committee will make recommendations to an emergency response team looking for a solution.