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NSW Coastline Management Manual

New South Wales Government
September 1990

ISBN 0730575063

Section 5: Hazard Management Options

5.1 COASTLINE HAZARDS

This section discusses the appropriateness in various circumstances of the range of management options, detailed in Appendix D, for addressing coastline hazards. Seven hazards have been identified along the New South Wales coastline. These hazards, described in detail in Appendix C, are:

5.2 HAZARD MANAGEMENT OPTIONS

Options for managing coastline hazards may be conveniently grouped into four categories:

Environmental planning options are described in Appendix D3 and are an effective means of avoiding or limiting risk to future coastal developments. The object of land use controls is to ensure that the type of development and potential damage is consistent with the hazard.

Development control conditions are described in Appendix D4. Such conditions are imposed through development and building approvals and are a means of reducing hazard on a site specific basis. Development conditions are especially relevant to limiting the growth in damage associated with new developments and redevelopments.

Dune management options are described in Appendix D5. Dune management activities are designed to maintain the integrity of the dune system as nature's last line of defence against wind and wave attack. Dune stability is based primarily on maintaining the dunes' protective mantle of fragile vegetation. The role of dune vegetation as a coastal "process" is described in Appendix B8. Dune vegetation is also briefly discussed in relation to Windborne Sediment Transport (Appendix B9), and Sand Drift Hazard (Appendix C5). Dune management is often referred to as a "soft" protection option, as opposed to the "hard" protection afforded by other protective works.

Works to protect hazardous areas of the shoreline are described in some detail in Appendix D6. The aim of such works is to eliminate or to reduce hazards to an acceptable level.

Hazard management generally draws on a mix of all types of options, which are incorporated into a coastline management plan.

Within each of the four categories there is a range of options which may be applied to management of hazards along the New South Wales coastline. These options are listed in Table 5.1. The broad advantages and disadvantages of each are briefly described in this section. Additional details are given in Appendix D.

Table 5.1

Hazard Management Options

Category Management Option
Environmental Planning Buffer Zones
Restrictive Zoning
Planned Retreat
Voluntary Purchase
Development Control Conditions Building Setback
Building Types
Dune Protection
Flood Mitigation
Foundation Design
Emergency Access
Relocatable Buildings
Planned Retreat
Dune Management Dune Management Planning
Community Involvement
Dune Reconstruction
Dune Revegetation
Dune Protection
Dune Maintenance
Protective Works Seawalls
Training Walls
Groynes
Beach Nourishment
Offshore Breakwaters
Artificial Headlands
Configuration Dredging

5.2.1 Environmental Planning

Environmental planning options provide measures to ensure protection of coastal land and restriction of development in hazardous sites, as well as encouragement of development in areas not subject to hazards so that hazards are avoided or minimised. Measures are detailed in Appendix D3, and include:

The underlying principle with these options is to recognise the environmental processes operating on the coast and "design with nature", ie to ensure development is sited so that hazards are avoided.

Alternatively, where this is difficult to achieve because of existing development constraints, the principle involves enacting policies to ensure development is carefully designed in or withdrawn from hazardous sites, in an equitable manner, so that hazards are minimised or avoided.

(a) Buffer Zone

The concept of a buffer zone is based on the philosophy that the coastal processes should be accommodated rather than prevented. The most basic form of accommodation is to avoid siting structures within areas affected by the various hazards. This requires the reservation or zoning of an appropriately managed area between the beach and development within which natural fluctuations can be accommodated. An appropriate buffer zone allows both for maintenance of natural beach amenity and also for the impact of natural processes without demands on the public purse for protection of structures.

When areas along the coastline are zoned to facilitate protection of existing vegetation communities, vegetated dunal systems or stabilised recreation areas, these areas provide an effective separation of developed areas from hazardous sites. The width of a buffer zone should take account of the natural foredune, and a buffer zone is most effective when it is sufficiently wide to allow for both the present fluctuations of the beach position with erosion and build-up, as well as likely future fluctuations.

Where high recession rates are experienced either the buffer zones should be wide enough to accommodate ultimate landward recession, or development landward of the buffer should be planned for only a limited time period in that position. Alternatively, other types of protective measures may have to be considered. Otherwise, the area of land from which development is excluded may be excessive.

Buffer zones have the advantage of providing for public foreshore access and protection while at the same time holding development back from hazardous sites and avoiding building damage. They facilitate the carrying out of effective dune management measures to further protect landward development from coastal hazards.

Figure 5.1 Buffer Zone, Maroubra Beach, Sydney

Figure 5.1 Buffer Zone, Maroubra Beach, Sydney.

(b) Restrictive Zoning

Restrictive zoning can be effective as a means of "damage control" to deal with coastal areas where previous zoning has granted rights for development in hazardous sites, i.e. where previous zoning decisions have not properly taken coastal hazards into account, or where high recession rates have eroded earlier buffer zones.

Such zonings can limit the amount of new development in hazardous areas and avoid increase of a hazard problem by new or increased intensity of development and keep hazard problem areas from becoming exacerbated by increased levels and densities of development. Provisions can include: requirements for development consent to be obtained to allow special conditions to be applied; establishment of building setback lines (See Development Control Conditions, Section 5.2.2.); limits on the number, size, scale and design of structures; etc.

Excessive restriction may generate compensation claims and care is needed in striking the right balance. A related approach is the application of a freeze on development (See Appendix D3) and requirements for an engineer's report on building and redevelopment proposals in areas of risk.

(c) Planned Retreat

Coastal land can be planned to permit development that has a limited life and this approach allows use and occupation of the coastal site until coastline hazards threaten or damage property. This permits a flexible approach in the future if hazards become more severe, for example in response to climate change, or in cases where there is moderate to high coastal recession.

At the time development is approved, a specified period can be identified before consent lapses. Alternatively, approval may specify that consent only remains valid while a beach erosion scarp does not encroach within a set distance from a development. At this stage, consent lapses and the structure must be moved back, relocated or demolished. (See Planned Retreat, Appendix D3)

Local planning instruments (LEP's and DCP's ) can be used to outline policies for planned retreat of development on hazardous coastline and can be coupled with other conditions on development and buildings to further limit potential damage to structures.

(d) Voluntary Purchase

Both the State and some Local Government bodies have adopted schemes to bring certain coastal properties, threatened by hazards, into public ownership. Following purchase, structures are usually removed and dune management techniques implemented to provide a stable coastal reserve at the site.

These schemes can include purchase of properties voluntarily offered for sale at equitable prices. This provides a cost-effective way of avoiding future damage to development subject to hazards. Voluntary purchase is also a means of removing anomalous developments from a rezoned area.

The costs of such schemes escalate as the level of development increases. Realistically, only small numbers of properties may be able to be acquired over a number of years due to constraints on available funding.

Other financial schemes may involve lease-back following purchase (see Appendix D4, Financial Measures,). These schemes may be coupled with other coastal management options, such as restrictive zoning, to increase their effectiveness.