The annual battle on the Rideau River pits thick frozen slabs against an arsenal that includes giant saws, sticks of dynamite and a bizarre boat with giant ice-smashing clods.
The late-winter ritual is intended to ensure ice won't clog the spring run-off, flooding homes and public buildings along its banks.
Beginning in February, city workers cut channels into the ice with large saws to prepare for demolition in early March.
"Following that, they'll drill some holes in strategic places so they can place dynamite," says Jason Staniforth, the City of Ottawa's manager of core roads.
"Then they use explosive charges to send the sheets of ice down the falls."
The $500,000 operation, paid for by the Rideau Valley Conservation Authority, includes a so-called Amphibex Excavator, designed and made in Canada by Normrock Industries.
The powerful boat, with its ice-smashing arms, was introduced in 1992 to cut down on the use of dynamite, which can damage ecological systems and surrounding infrastructure.
The Amphibex also features a hydraulic boom with a bucket that scours the river, bashing through the ice.
Staniforth says the Amphibex has replaced much of the blasting work on the river.
The annual ice-smashing exercise in Ottawa has been in effect for more than a century. The city expects to wrap up the operation by April.