ORC develops innovative heli-gauging technique for major floods

An Otago Regional Council (ORC) hydrologist has developed a world-leading, innovative method of measuring high river flows during a flood, using a modified kayak.

Paul Hannah will travel to Melbourne in August to make a presentation to the Australian Hydrographers Association on the helicopter gauging method and the kayak.

Mr Hannah has already made a similar presentation to the association’s  New Zealand counterpart.

ORC chief executive Graeme Martin said hydrologists had always strived to safely measure flood flows in larger rivers and take as many measurements as possible during significant flood events.

Mr Martin said Mr Hannah and his ORC colleagues had achieved a technological breakthrough in developing their helicopter-deployed kayak, which is equipped with modern sonar measuring equipment. In doing so they had been highly successful in merging various technologies into one, he said.

Mr Hannah said the project took root when he and his colleagues in ORC’s Regional Services unit decided they needed a specialised boat or platform to house an Acoustic Doppler Current Profiler (ADCP).  This is a device that uses sonar to accurately measure water velocity and depth.

“It is like a very advanced fishfinder which we drag across rivers to measure the flow,” Mr Hannah said.

“The platforms used to carry ADCPs currently on the market do not handle New Zealand flood conditions well, so we designed and built our own from a modified kayak.”

It was designed so it could be safely towed across floodwaters either by hand, off the side of a jet boat, below a cableway, or from a helicopter.

“The boat performed so well that we trialled towing it from a helicopter. Industry experts in America, Australia, and here in New Zealand tell us this may be the first time a helicopter has been used to gauge river  flows with an ADCP anywhere in the world,’” Mr Hannah said.

Pilots from Helicopters Otago Ltd, which has a long history of specialist flying, including long-line and live-line work, were involved in the trials.

The volume and accuracy of data acquisition would exceed anything previously possible, and would lead to increased flood modelling accuracy,  Mr Hannah said.

The new platform has performed well to date when measuring flood flows. Its design improves the quality of data collected and makes it safer to deploy in challenging flood conditions than current designs on the market

The new gauging method is also cost-effective and safer than traditional methods, because it does not require staff to be on the water during a flood. ORC field hydrology staff will be able to access sites during a large flood event even when access roads are closed due to flooding.

Mr Hannah received a cash prize for the best presentation at a NZ Hydrological Society conference titled 'Change and improvement in operational hydrology.'

He will use the prize to help fund his trip to Australia in August.