DEAR News Of The Area,
PROPERTY and Development NSW has just released technical reports supporting the rezoning of land currently zoned RE1 Public Recreation and SP2 Infrastructure to allow for the construction of multi-storey development on Government-owned land at the Coffs Harbour Foreshores.
One of the reports is a Coastal Risk Management Assessment by consultants Hasconing Aus.
Their modelling of future shoreline movement assumes there is a “Certified Engineered Seawall” along 130m of South Park Beach (also known as North Wall, Dog Beach) to prevent recession of the coastline and provide protection to land behind that is integral to the overall planning proposal.
It also recommends that consideration be given to extending the wall by a further 140m to provide more protection in the long term.
The additional length is not mandated.
Depending on the degree of exposure, a typical open coast seawall, capable of withstanding long-term recession and sea level rise, would need to be constructed to a height of approximately 6-8m above mean sea level, with an appropriate core and large armour (approximately 1.3 m diameter).
It would typically extend 15m horizontally from the crest of the dune across the beach and to a depth of approx 2m below mean sea level.
The Hasconing report implies that a suitable Engineered Seawall actually exists (the crest is only 4m high in places) and that the existing rock wall could be adequately maintained/adapted to comply with design standards and accommodate a rising sea level scenario.
Any such adaptation could potentially require a major reconstruction and/or raising of the existing wall.
This may require Development Approval which can’t be guaranteed.
Furthermore, it is assumed that the retention of a seawall (or a further 140m extension) is an acceptable long term management strategy for this beach, which may not be the case.
The construction of sea walls is known to accelerate beach erosion resulting in a partial or possibly complete loss of beach, particularly if sea level rises.
The cost of adapting the existing section of wall to comply with certification standards under a rising sea level scenario is unknown.
A conservative estimate to construct an additional 140m of Engineered Seawall (based unit rates from a 2021 NSW Gov report for Wamberal) is in excess of $2.7 million.
The ongoing maintenance cost of 270m of seawall would be approx. $50,000/yr.
The adoption of a seawall as a coastal zone management option is completely out of step with contemporary Coastal Zone Management Principles and is only used as an absolute last resort to protect valuable assets that have been inappropriately located too close to the shoreline and are under threat from loss or damage.
Such an option should never be considered to support the rezoning of land that is largely undeveloped.
After the recent storms, North Wall Beach is inaccessible at high tide.
Under a rising sea level scenario, the situation will get gradually worse until there is no access at all.
It is likely there will be no beach along the entire length, at any tide level, and the waves will be breaking against the sea wall.
It is time to speak out now against this poorly considered rezoning and seawall upgrade proposal. There are other important and viable coastal management options that need to be considered to ensure our prized beaches remain in a usable and ‘natural’ state before we lock in the long- term loss of North Wall/Dog Beach.
Regards,
Bruce FIDGE,
Retired coastal engineer,
Coffs Harbour.
