Munich's city government and a local surfing organization are scrambling to restore a wave credited with helping establish the freshwater surfing movement, which disappeared after annual drainage and cleaning late last week.

Authorities plan to experiment with changing the water levels, in the hope that the currents realign. 

"The many parameters that cause the wave in the water flow are being examined and adjusted accordingly," Mayor Dieter Reiter said. 

Known as the Eisbachwelle (icy stream wave) in German, the wave is located on a man-made stream funneled off the River Isar in the city center park called the English Garden. 

Munich's water authorities would start measuring the water flow, and artificially raising the water levels. 

"Using these results we will jointly establish how other redirection efforts can change water flow and volume levels, and how a surfable wave can be built up," the city government said. 

Wave vanished after routine drainage and basin cleaning 

What exactly caused the wave to disappear is not clear. After what city authorities say was routine cleaning and removal of sediment from the river basin, with no changes made that should have affected the water's flow, the swell did not reform as water was again allowed into the stream on Friday. 

At present there's a simple and steady flow of water of no use to surfing enthusiasts.

SurferToday.com refers to the Eisbachwelle as "the mother of all river waves," after surfers created it in 1972 by placing concrete blocks on the canal bed to create the strong current. 

Strictly speaking, surfing at the site was only legally sanctioned in 2010, long after it had become a noted attraction. 

Surfing was stopped earlier this year for renovations, after an experienced surfer died when her leash is thought to have become entangled with detritus on the basin. The city subsequently altered rules and banned surfing at night. However, the wave did flow again as normal after the renovation work was completed and the wave reopened in June.

Mathias Schmidt from a surfers' interest group in Munich, IGSM, said his organization and city authorities were working together on efforts to restore it. He said the desire to recover the tourist trap had also motivated the Bavarian capital, not just local surfers. 

Edited by: Zac Crellin