Height is right to make pool clean: researchers

Luan Nguyen and Dan Courtney are confident the height differential between the sea and the proposed pool would be sufficient to flush it clean. Picture: Andrew Ritchie d411354
Luan Nguyen and Dan Courtney are confident the height differential between the sea and the proposed pool would be sufficient to flush it clean. Picture: Andrew Ritchie d411354

‘That’s enough of a difference to be a driver of a very systematic flushing of the whole pool,’ concept design engineering student Dan Courtney said.

At the University of WA’s Centre for Water Research last week, Mr Courtney and wave researcher Luan Nguyen briefed pool proponents, lifesavers and mayors on wave and sand patterns and a concept design for the pool.

Cottesloe Surf Life Saving Club member Tom Locke has called for the pool ever since a shark attack that killed Ken Crew at North Cottesloe in 2000.

Mr Courtney said an artificial reef north of the groyne’s tip would alter waves and increase water pressure through the permeable rock wall enclosing the sand-bottom pool.

Water would enter and leave through underwater culverts on the west and northern sides of the addition to Cottesloe Beach facilities.

Mr Courtney’s study of 12 building materials found the current groyne’s rubble mound construction was the best for absorbing wave energy, longevity and used local materials, because a smooth wall allowed waves 5m up its sides, compared with 2.5m for a rough surface.

It is estimated the $1.65 million pool would require 18,000 tonnes of granite, after a $150,000 engineering design phase.

Centre for Water Research director Jorg Imberger recommended the design be tested with wave data for a year, partly to judge if weed from north-west winds and storms could affect the pool.

‘If there’s a real big storm, there may be a little pool maintenance involved,’ Dr Imberger said.

Cottesloe Mayor Jo Dawkins, whose council has a $15 million foreshore redevelopment plan that includes an unspecified design for a sea pool, said the centre’s work had saved money and councillors could be briefed on the concept design early next year.

‘I’m going to approach schools, parents and our club’s nippers to tell them about it even before then,’ Mr Locke said.