Historical beach study recommended dune construction

A beach erosion study from the early 1970s indicated that the ongoing erosion issues at Ettalong, Ocean Beach and Umina had a long history.

It recommended the curtailment of the development of a nearshore channel against the Ettalong shoreline and argued that soft management techniques such as dredging, beach nourishment and dune construction were more suited to achieving better beach amenity at Ettalong.

The 126-page report from the Coastal Engineering Branch of the NSW Department of Public Works started with the statement in its foreword: "Ettalong Beach has suffered various erosion problems since the 1940s which have resulted in the construction of piecemeal protection works.

"The erosion has worsened since the construction of a groyne field in 1972.

"In 1973, in response to a request from Gosford Shire Council, the Minister for Public Works formally recognised the need for a detailed study of the erosion problem in the Ettalong region as a whole."

The Minister may have recognised the importance of the study but it was not commenced until September 1976.

The study included a geological survey to define the boundaries of sediment movement within the Ettalong estuary.

A conceptual model was developed to describe the sediment dynamics within the natural boundaries which was then verified using historical data, aerial photos and the examination of the impact of human intervention.

Data on currents, tides, waves, shoal mobility was collected in the field and used to evaluate time scales of erosion processes and rates of sand movement.

"From this investigation, a number of significant conclusions were reached,' the report said.

The first conclusion was that erosion events in the Ettalong region were inter-related and not soluble in the long-term by means of isolated remedial work.

"Erosion is not primarily caused by the natural loss of sand from the estuary as the quantity of sand contained between the Rip Bridge and the outer edge of the Ettalong Point shoal in Broken Bay remains essentially constant," the report concluded.

"Sand contained within this estuary system is quite mobile, moving from the outer shoal to the beach and thence back to the outer shoal via the tidal channels.

"Erosion is attributable to the fact that this circulatory pattern is variable in time, rate and location, resulting in beach fluctuations.

"These fluctuations can be increased by variation in channel alignment within the estuary," it said.

The NSW Government report set out a Beach Management Program and stressed that there should be "continuing management of this fragile beach in the future".

Strategies recommended in the report, over 40 years ago, included beach nourishment and dredging.

SOURCE:

Document, 1976

Ettalong Beach Erosion Study, NSW Department of Public Works

Reporter: Jackie Pearson