The series of black-and-white squares appeared between David St, Caversham, and Second Beach Rd, at St Clair, and along Forbury Rd.
The Otago Daily Times observed yesterday they appeared to line up with the Forbury aqueduct.
Dunedin City Council Three Waters group manager John McAndrew confirmed the markings were part of survey work being carried out for the planned Forbury aqueduct upgrade.
They enabled use of a drone to collect some survey data, reducing the need for traffic management and associated costs, he said.
An upgrade of the aqueduct was part of a package of measures approved by the council last year to support flood alleviation in the short term.
Construction is expected to begin next year.
Required changes to the Second Beach outfall have not yet been confirmed.
"Once survey work is completed, consenting requirements have been confirmed and hydraulic modelling is complete, we will move into a design phase which will give us a better idea of costs and timeframes," Mr McAndrew said.
Another part of the planned package is diverting the Bay View Rd and New St stormwater systems to a new pipe directly to the Portobello pump station.
Mr McAndrew said the Portobello Rd project had been awarded to a designer and design work was under way.
"A separate package of enabling works will move the wastewater pipes in the area to facilitate installation of the additional stormwater pipe," he said.
Construction work could start in mid-2026, followed by installation of the new stormwater pipe.
The other short-term measure approved by the council last year was about diverting flow from Hillside Rd to the Orari St outfall through a new pump station.
This was considered to involve some complexity.
"The Hillside Rd work is still in the early stages of survey and investigation work and there is much additional work to follow, meaning construction is likely to be a number of years away yet," Mr McAndrew said.
