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".
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.
The high beach profile (the level of sand) on Ocean Beach for the first half of the year has proved invaluable in recent weeks. While there was some sand loss in the early part of winter, a good deal of the very healthy reserves of sand remained until recently. Much of it was stripped away by the strong winds and high tides experienced during July. With the removal of that sand buffer, a section of the rubble wall has been uncovered and there has also been damage to the Reno mattresses that provided protection to the toe of the dune at Middle Beach. The Reno mattresses are being repaired, the rubble wall reinstated, and sand levels at Middle Beach are being topped up on an 'as required' basis.
That maintenance regime will be continued while the information gathering process draws to a close. A Project Team has been appointed to study the information that is being collated for the Long Term Management Plan, and the program for completing the studies and preparing the Plan remains on track.
Encroachment by heavy seas checked
ODT By Allison Rudd on Mon, 27 Jul 2009
It was estimates $50,000-$60,000 had been spent at Middle beach in the past few days trying to protect rock mattresses laid at the base of the dunes, which had been exposed by last week's heavy seas, and trucking in sand dredged from Otago Harbour and tipping it down the face of the dunes.He estimated the width of the dunes had decreased by 2m-3m in the past two years.The end of Moana Rua Rd fell away last Thursday, and the face of the dunes was now close to a large fence erected in 2007 to stop people from using a dune-top track which has also since succumbed to the sea.
It was difficult to believe the Moana Rua surf club building had once sat between the end of the road and the beach, he said.
"When we demolished that [in 2001] there was a lot of criticism. People said it would have made a good restaurant. But the area it was sitting on does not exist any more."
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.
UPDATE 25th July 2009 article from ODT
"It's as serious as it's been since the emergency [in 2007]."
Contractors next week would build a new mattress and place it behind and beneath the existing ones.
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)
The usual winter weather has caused a significant reduction in the beach profile (sand levels) on the Ocean Beach.
There is no cause for concern, but the area is now being monitored more frequently. The Council's applications for retrospective consent for emergency works on the beach (carried out in 2007 and 2008) have now been heard by the Otago Regional Council, and their decision is expected shortly. Much of the background data and studies needed for the Long Term Management Plan have been collated, and a Project Team been appointed to review this.
Further information is still coming to hand, and the Project Team's review should be completed before the end of the year. The draft Management Plan will then be submitted to the Council and released to the public for consultation.
The City Council's applications for retrospective consents for the erosion control work at Ocean Beach have been scheduled for hearing by the Otago Regional Council at the end of June. (Specific details of those works were set out in the February 2009 update.). As previously advised, most of the comprehensive studies needed before the Long Term Management Plan can be prepared are now to hand. The studies will be completed later this year. In the near future, a Project Team will be appointed to consider the data that has been collected to date.
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.
There has been good progress with the various studies required before a long term plan for Ocean Beach can be developed. Many of these studies are now to hand, and the remainder should be completed over the next few months. When the information from all studies is available, options for a long term plan for the Ocean Beach will be identified. Meanwhile, favourable weather conditions over the last few months have meant that overall sand levels on the beach are as high as they have been for decades.
This is especially pleasing, as it should allow time for the Council to identify and measure all matters that may affect the management plan for Ocean Beach, rather than risk having to respond to any individual issue in isolation.
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.
The Council will be carrying out the following surveys and assessments in order to gather as much background information and data as possible.
Information on dune position, beach elevations and volumes over the total four-kilometre length of Ocean Beach is required for a number of reasons including:
Information on the near-shore seabed topography is required for input into modelling of wave refraction, sediment transport, storm response and recovery, and sea level rise effects. There is existing information showing levels at 10 metre depth intervals, which is sufficient for offshore areas, but not detailed enough for the near-shore areas for depths less that the 20 metre contour.
There was useful data and information on coastal process and beach responses in the material presented as evidence to the St Clair Sea Wall and Tahuna Outfall project's consent applications. This information as the Council proceeds on additional investigations, as it may provide some or all of the required information.
Information on sediment size and sorting is required for input into the sediment transport and beach response modelling, and for evaluation of some possible protection options, such as beach re-nourishment.
Changes in near-shore bar formation and rip cell location are important for determining the presence and location of erosion "hot spots" along the shore. Due to the difficulty and costs of surveying in the surf zone, it is proposed that the best way for collecting information on the nature and scale of these changes is to establish a Cam-Era site. This is the automated collection of digital images of the shorelines and surf zone at hourly intervals from a fixed site. These are then rectified and analysed by specialised computer software to quantify dynamic changes in beach, bar, and surf behaviour. The local site requirements include sufficient elevation, power and telephone supply. The maximum distance of a camera to the beach under investigation is in the order of two kilometres.
The mapping of past shorelines over the whole length of Ocean Beach will identify the scale to which human interventions have affected shoreline position and shape, such as the influence of the St Clair Seawall, Middle Beach landfill and sports field development activities, and the construction of John Wilson Drive.
This would entail a ground penetrating radar survey of the dune environment at Kettle Park and John Wilson Road to determine the extent of rubble buried under the dune system that may be exposed with future shoreline movements (also see Historical/cultural/social research below).
This is needed to reduce uncertainty about the nature of the inshore wave climate and the magnitudes and directions of sediment transport in various wave conditions. This information is required for inputs into storm response and long-term plan shape evolution modelling, and for the evaluation of different long-term management options.
Storm response modelling will qualify the range of potential responses of the beach and dune environment to storm events. These responses will vary depending on the size and direction of the storm event, and the antecedent beach conditions (eg height and volume). This modelling will include any changes to water levels and wave climate as a result of predicted sea level rise. The output of this type of modelling is required to test the likely success of the various long-term solutions and their likely impacts on the beach under these conditions.
Future plan shape evolution modelling is required to predict how Ocean Beach may respond in plan shape in the future to the forecasts for wave climate, sediment supply and transport, and sea level rise over the next 50 years. The modelling can include plan shape responses to future management options such as additional seawalls, groynes, beach re-nourishment, and offshore breakwaters.
A number of the possible long-term options will require additional volumes of sand to be placed on the coast or in the near-shore at Ocean Beach for beach re-nourishment. There is a need to investigate risks to adequate supply, including volume, suitability such as grain size, colour and lack of contaminants, transport routes and methods, whether road, pipeline or boat, dumping location such as behind or on the beach, or in near-shore and possible storage options.
This will be a report summarising the data collection and modelling. It will present these in the form of a SWOT (Strength, Weakness, Opportunities and Threats) analysis.
Research into the historical, cultural and social aspects of Ocean Beach is necessary. It should be carried out as a project to produce a bibliography of historical and cultural information on Ocean Beach, available to the project team responsible for drafting the long-term plan.
This research also satisfies the recommendation from DTec Consulting Limited/Shore Processes and Management Limited for a historical review of documents, files and photos of Ocean Beach Dunes and hinterland including Kettle Park Landfill and Sports Field Development. This allows a more complete understanding of the modification of the Ocean Beach dunes by human intervention and better understanding of the changes that have lead to the current situation.
An ecological assessment will be carried out to provide advice on options for appropriate ecological management for the rehabilitation of areas likely to be affected by physical works, re-nourishment programmes and recreational use.
The emergency works and holding pattern include the following:
Time heals all wounds, nature is taking its' course in replenishing the sand at ocean beach.
Cam-Era – St Clair A
Cam-Era – St Clair B
Updated every 30 minutes.
from NIWA website
Ocean Beach is a 3 km long sandy bay in south Dunedin running from the St. Clair headland in the west to Lawyers Head in the east. The beach, located just 4 km from the centre of Dunedin city, is the main recreational beach in the region, being popular for surfing, swimming, and walking. At St. Clair, the Esplanade is popular with visitors for the numerous restaurants and cafes, while in the centre and eastern end of the bay the former back dune environment has been developed into sports fields and golf links.
The beach faces due south, and is exposed to the dominant south westerly winds blowing off the Pacific Ocean and frequent high energy southerly storm events. Sand is transported to Ocean Beach by a prevailing southerly current and the dominant southwest swell conditions.
In pre-European time, the Ocean Beach area was characterised by small sand deposits at the western end, increasingly large sandhills to the east, and a hinterland dominated by a lagoon and swamps. As early as 1876 sand was being removed from the dune to fill the low-lying hinterland to meet the growing needs for housing in the developing city. There has also been a long history of coastal erosion issues at Ocean Beach: breaching of the dunes producing sea flooding in the low-lying hinterland suburbs was reported in the 1880s and 1890s; a seawall has been present at St. Clair since 1888; and dune stabilization using brush fences and marram plantings was first started in the 1890s. These erosion issues have continued at periodic times over the last 100 years, with episodes of rapid dune erosion being interspersed with periods of stability and dune growth. The last major erosion episode occurred in 2007, when up to 20 m of dune retreat was experienced, and an estimated 200,000 m3 of sand was removed from the dunes and beach. As a result of this erosion, the DCC were forced to undertake emergency works to protect both public and private assets.
As a consequence of the 2007 erosion episode, the DCC have embarked on an investigations programme to better quantify the nature and magnitude of the coastal processes operating within Ocean Beach, which will allow better decisions on future beach management to be made. The Cam-Era project is part of this investigations programme, producing much needed real time information on wave conditions, movements of rip currents, and beach responses. Without the Cam-Era site, this type of data would only be available from irregular visual observations, photographs, and beach surveys, none of which are able to supply a continuous picture of coastal processes and beach responses.
Favourable weather conditions over the summer to date have meant the volume of sand on the beach continues to rise steadily.
In the meantime, focus group meetings with key stakeholders continued during December and January, with the final group of meetings with these stakeholders scheduled for mid- February. Ecological studies (fauna and flora) of the area has now been completed.
That report on the area's ecology will be the first of a number of comprehensive reports to be received that will eventually provide the information and data needed for the draft plan for Ocean Beach.
