Global Warming and Port Phillip Bay

Author:  Mary Rimington
Date:  10 October 2001
Submission:  An edited extract from the MBCL Submission to the Kingston Planning Scheme (Amendment C8)

Although there has been in excess of thirty years of warnings of the impact of global warming and climate change on the heavily populated coastal fringes of Port Phillip Bay, especially from Aspendale to Patterson River, no attempt has been made to curtail development on the eastern most vulnerable side of Port Phillip Bay.

Two of Australia’s internationally renowned scientists, both previously based at the CSIRO Atmospheric Research Centre located in Aspendale, Dr Graeme Pearman and Dr Barrie Pittock were issuing warnings of climate change impacts in 1986.  The scientists’ warnings were heeded by the former City of Chelsea, who produced their own Greenhouse Strategy Report in November 1990.

The section of beach from Mordialloc Creek to Patterson River is one of high sensitivity, with high wave energy and strong littoral processes, and minimal buffers to absorb changes close to residential development and infrastructure on the foreshore.  Over the years there has been much destruction of buildings, for example:

  • A concrete block structure at the end of Williams Grove, Bonbeach due to wave action and erosion in 1970;
  • Chelsea Sea Scouts building demolished due to erosion and wave action in 1978;
  • Loss of bathing boxes from behind the seawall at Gnotuk Avenue in the late 1970s due to loss of beach and undermining of the seawall; and
  • Loss of several Chelsea bathing boxes in high storm conditions in 1980.

CLIMATE CHANGE AND COASTAL MANAGEMENT

CSIRO Division of Atmospheric Research report states that:­ “The inundation of land by the sea and the predicted average sea level rises will have sufficient obvious consequences to immediately raise interest in the subject of coastal impacts and management and includes a wide range of possible first order impacts that need to be considered”.

These are:

  • Accelerated recession of coastlines;
  • Narrowed beaches;
  • Flooding of low-lying coastal plains;
  • Intensified erosion, structural damage and marine flooding in storm surges; and
  • Rise of the water table in coastal areas.­

Each of these impacts carries with it secondary impacts, which in a particular area relate to the continued viability of urban land use or natural ecosystems.  Planners in particular, with regard to the eastern side of Port Phillip Bay, must be cognizant of the climatic, sea level and direct carbon dioxide effects that might influence their predictions.  They need to commence site-specific studies required to integrate the complex interactions of sea level rise and climate change into useful predictions for the future (1).

Dr Pittock adds further evidence with his report into the Greenhouse Effect.  He claims that:

Coastal management, depending on the magnitude of the sea level rise, may be greatly affected.  Remedial action could be extremely costly, with major capital works necessary to protect low lying areas and especially water-front buildings and marinas near coastlines.  Beaches and holiday resorts may be badly affected (2).

What needs to be remembered is that although both of these scientists are suggesting that sea level rise might not be apparent for a decade, global warming is causing climate change which is already having an effect on the vulnerable eastern Bay coastline, through more frequent and more severe storm surges.

Storm, Kerferd Road Pier, 2005

Storm, Kerferd Road Pier, 2005 (storm removed Middle Park beach)

Should further confirmation be required as to the effects on the fragile coastline, the Victorian Coastal Vulnerability Study (1992) highlights the fact that the most vulnerable area in danger due to storm surges is the section of the Bay from Mentone to Frankston, and yet this is the area that the present Government is promoting for tourism, medium to high density housing, aquaculture and marinas.  The accompanying article and photos are evidence of the erosion problems which have occurred in previous storm events (3).

STORM SURGES

Storm surges are temporary elevations or depressions in sea surface height driven by surface winds and changes in atmospheric pressure.  Their severity depends on the strength and duration of the atmospheric disturbance and structure of the coastal terrain.  Severe storm surges can cause inundation of low lying coastal plains and flooding of river systems.  Combined with wind generated wave action, storm surges can contribute to coastal and estuarine erosion (4).

Existing flooding situations can also be prolonged or worsened by storm surges.  This can happen in situations when the storm responsible for the surge also produces extreme rainfall, or if a storm surge generating system occurs soon after a severe rainfall event.  In either circumstance, the storm surge can elevate sea levels in the vicinity of river outflows, thereby reducing the drainage rates and contributing to flooding of river systems and flood plains (5).

The set of circumstance referred to above occurred in 1994 in a section of Port Phillip Bay from Mentone to Frankston when heavy rainfall, westerly winds and a king tide combined to cause severe erosion of the Mentone, Parkdale and Aspendale foreshore, and flooding upstream in MordiallocCreek.  Global warming has resulted in stormier weather and a greater number of severe storm surges on the eastern side of Port Phillip Bay.

The Environment Protection Authority (EPA) in 1996 modeled three sections of the coastline of Port Phillip Bay and highlighted the sensitivity of the region to the different prevailing wind directions.  In general, the western side of the bay was less sensitive to wind strength changes than the eastern side, since storm surges tend to be caused by westerly winds.  Considerable sensitivity was apparent within the Mordialloc section (6).  The report states that an event such as the 1934 flood, which produced both extreme rainfall and storm surge, could cause failure of the existing flood protection system, therefore leading to far greater flooding.

It is worth noting that approval is being given by the local council for two residential developments on the flood plain on the north bank of Mordialloc creek.  One development is for 700 houses (Kingston Lodge, also known as The Waterways), and the other on the former Epsom racecourse for 500 houses.  The Epsom racecourse flooded to a depth of two metres in both 1934 and 1952 floods.

OVERDEVELOPMENT AND FLOOD MITIGATION

In 1871, the flood-plain of the Carrum Carrum swamp was drained for agricultural purposes, but as development encroached, severe floods in 1934 and 1952 alerted planners to the danger of permitting development in flood prone areas.

In 1954, the Melbourne Metropolitan Planning Scheme Report compiled by the MMBW, referring to the location of future residential areas, warned:­

Except for the low-lying areas along the Yarra River and between Mordialloc and Frankston, there are no substantial portions of the metropolitan area… (that) are physically unsuitable for residential purposes.

Despite this warning, development of the flood prone areas continues, ultimately to require millions of dollars to replace the old, inadequate drainage system.  Added to the problems of overdevelopment of the foreshore and green wedge is the potential impact of increased storm surges due to climate change and the Victorian Channel Authority’s (VCA) plan to dredge the shipping channels in Port Phillip Bay.  Coupled with this is the proposal to deepen the Rip at the entrance to the Bay resulting in a possible sea level rise, especially during high tides.

The Channel Authority advises:

The associated studies will include investigations into the hydraulics, including coastal processes and possible effects on sea level and beaches of a dredging program.

Kingston’s 13 kilometer coastal strip and flood prone areas in the Mordialloc are designated as ‘Increased Diversity’ areas, with a subsequent increase in impervious surfaces.  Given the readily available warnings about land subject to flooding on the most vulnerable, eastern side of Port Phillip Bay, nomination of these locations as increased density areas is indicative of questionable planning procedures.

Corner of Governor and Springvale Roads, 1998

Corner of Governor and Springvale Roads, 1998

GREENHOUSE STRATEGIES

The (former) City of Chelsea report describes the effects of Climate Change and the issues confronting this bayside council in the event of storm surges and beach erosion, something which the Council had to address in 1970 when foreshore structures were destroyed in severe storm events (7).

This study raises important issues of who is responsible when bayside residents suffer property damage as a result of a storm event.  The estimated value of residential land near the foreshore reserve (beach) in the City of Chelsea in 1990 was estimated to be $150 million, but would be worth much more today.  It is obvious therefore, with the impact of climate change predictions, that there is a need to address planning issues which could otherwise lead to law suits against Council, if losses to real estate occurred in future.

Quoted in this report are the proposed actions of the former Cain-Kirner Labor Government with regard to financial responsibility for storm damage.

“The Government strategies for dealing with rising sea level could range from:

  • Stabilization with appropriate long term protection;
  • Controlled retreat;
  • Protection for a certain time only; and
  • Letting nature take its course”.

The document advised that options for minimising damage and destruction would be identified and eventual government commitment to protective works on public or private property determined after consideration of issues, such as the extent of erosion, economic factors and costs, and joint private and public funding.  The protection and maintenance of the public coastal reserve would be given high priority, but no commitment was given ‘as of right’ to the protection of private property at Government cost.  The Government report also advises measures would be introduced to ensure that “inappropriate coastal development does not occur in future”.

In contrast to the forward looking policy, the Bracks government, through its Victorian Coastal Strategy, is encouraging medium density residential development in this and other sections of the Port Phillip Bay foreshore, and is approving the construction of marinas and restaurants on the foreshore.  In the City of Kingston, some existing structures on the foreshore are to recycled as cafes and kiosks, despite the fact that Mentone, Parkdale and Aspendale beaches have been renourished at considerable cost.  Another consequence of climate change for bayside councils could be alterations to insurance cover.

URBAN PLANNING AND GREENHOUSE ISSUES

Chelsea Council was aware of the pressure of increased density development on the primary dune and felt that the Melbourne Metropolitan Planning Scheme, as it was then, required urgent review to reflect serious issues raised by greenhouse predictions.  A reduction in development density on the foreshore was necessary.

Council’s report stated, “To retain the Residential Code and ignore current scientific knowledge and predictions of the greenhouse effect could be considered a failure of Council’s responsibilities and arguably could lead to law suits against Council if losses to real estate occurred in the future. Indeed, many foreshore communities both in Australia and overseas are already planning for the greenhouse effect and amending planning schemes and building requirements accordingly.  It is considered that the time has come for the City of Chelsea to do the same” (1990, p.16).

Unfortunately, the amalgamations occurred in 1994 and Chelsea Council was swallowed up by Kingston.  This important document disappeared, and development over the last 17 years has escalated on this vulnerable section of Port Phillip Bay foreshore, on the City of Kingston’s watch.

The Victorian Government also issued a report, The Greenhouse Challenge in June 1989 as a response to climate change and implications for coastal regions.  Strategies proposed included:

  • Stabilisation of the foreshore with appropriate long term protection;
  • Controlled retreat with protection for a certain time only; and
  • Letting nature take its course.

Furthermore, the protection and maintenance of the public reserve would be given high priority, but no commitment was given as-of-right to the protection of private property at Government cost.  The report also advises that measures would be introduced to ensure that inappropriate coastal development did not occur in future.

Chickens have indeed come home to roost.  Eighteen years later, none of the above has happened.  The State government has encouraged increased density development on the sensitive coastal fringe, high priority is being given to protect private property only on the foreshore, either through geo-textile sandbags or a sloping bluestone wall at an exorbitant cost.

An article in the Waves periodical raised the issue of builders, planners, engineers and architects being sued if beachside residents fail to find an insurer, if their homes are destroyed or damaged due to sea level rise or storm surges.

The sudden burst of activity for foreshore protection work at North Aspendale and other bayside suburbs is said to be to indemnify councils or exempt them from legal action, should foreshore residents’ private property be destroyed or damaged.  Will council now ensure that there is no further inappropriate development on Kingston foreshore requiring costly erosion control work in future?


LIST OF REFERENCES:

  1. Pearman, G.I., (1986) “Climate change and coastal management” in Planner, Dec.
  2. Pittock, B. (1987) “The greenhouse effect” in Engineers Australia, Feb 6.
  3. Coastal Investigations Unit (1992) Victorian Coastal Vulnerability Study, Environment Protection Authority & Port of Melbourne Authority, Melbourne
  4. Environment Protection Authority (1996) Extreme events and the impact of climate change on Victoria’s coastline: Report to EPA and Melbourne         Water (Publication 488), Environment Protection Authority, State Government of Victoria, Melbourne, p.4.
  5. Ibid. p.5.
  6. Ibid. p.64.
  7. City of Chelsea (1990) Greenhouse Strategy Report, November.

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