Cr Larry Dallimore said Westshore beach's struggle to keep sand was due to dredging to allow ships into the Napier Port.
"The near shore seabed off Westshore beach has been seriously damaged due to the port channel interrupting beach replenishment and the annual nourishment with incompatible loose shingle in volumes less than annual losses."
"Currently, sand is dredged every two years and dumped north of the Surf Club, about 500m off the beach in around 4m depths, because the dredges cannot discharge closer.
"Existing consent permits do not cover the southern end where the near shore seabed is seriously eroded due to years of replenishment starvation," he said.
But Napier Port Chief Executive Todd Dawson said a significant body of work had been done on the coastal processes impacting Hawke's Bay during the development of the 6 Wharf proposal.
"That work and work before it showed that there are many causes for erosion at Westshore, but there is consensus among coastal experts that the main cause of erosion at Westshore is the 1931 earthquake," Dawson said.
The dominant reason for the "chronic" erosion at Westshore "stems from the misalignment of the beach and near shore seabed resulting from uplift that accompanied the 1931 earthquake", an analysis by Dr Peter Cowell had confirmed.
"Readjustment would have initiated immediately after the uplift, but at first would have been manifest as coastal accretion, then a period of relative stability punctuated by periods of acute erosion."
Chronic erosion at Westshore since about 1980 was "an expression of the final phase of natural readjustment", Dawson said.
He said studies showed that Napier Port's breakwater had a minor contribution to erosion at Westshore, but it also sheltered the beach.
Because sediment movement was a constant process on the Hawke's Bay gravel coast, sand could settle temporarily on Westshore Beach between swell events before drifting north, Dawson said.
