Now, however, new and more accurate calculations using state-of-the-art "Lidar" technology show it will take at least 2 million cubic metres of sand to stabilise the beach, or four times the 500,000 cubic metres that the City of Newcastle was using this week as its estimate.

Lidar (the name is a shortening of "light" and "radar") is a digital 3D modelling system that is leading a revolution in a host of disciplines, including map-making. It's the same technology that archaeologists are using to find lost cities under African sands and South American rainforests.

Tackling the Stockton problem, Peter Jamieson - the founder of Newcastle "spatial analytics" firm Anditi - and University of Newcastle engineer Ian Taggart, are using Lidar to track two decades of sand movement, resulting in a new understanding of the likely factors behind the present crisis.

The Nobbys and Stockton breakwalls are widely accepted as causing a local interruption to the general south-to-north movement of sand along the NSW coast.

But Anditi's 3D maps present a more complex picture, showing a "scour depression", or "plughole" at the end of the Stockton breakwall, pulling sand away from the rock-stabilised beachfront.

Mr Jamieson founded the environmental consultancy Umwelt before selling it to concentrate on Anditi, and his work is highly regarded. A report of his from 2002 identified two eras of erosion at Stockton.

The first, when the breakwalls were built, ended in about 1900. The present difficulties, he wrote, began after the harbour was deepened in the late 1970s and early 1980s to accommodate bigger coal ships - a finding with potentially significant implications should a Newcastle container terminal aimed at ultra-large vessels ever come to be.

In the meantime, the Jamieson/Taggart work should be officially reviewed - and replicated, if necessary - to reinforce its legitimacy. This would give us new parameters for offshore dredging, which could be funded, at least partially, by port users, primarily Hunter coal exporters.

A slice of existing royalties, or a levy of just 30 cents a tonne, would raise the previously quoted cost of $50 million in less than a year, providing a financial fix for a Gold Coast-style solution to Stockton's problems.

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