Heavy rains and flooding caused irrevocable damage to a popular Calgary park, including washing away half its trails and damaging the rest.

Officials said the deluge that wreaked havoc in Alberta over the past two weeks has permanently altered Fish Creek Park, a provincial facility in the southern end of the city.

Flooding destroyed the park's boat launch and seven pedestrian bridges, rendered seven other bridges unsafe and damaged picnic areas, a popular swimming spot and wildlife habitat.

"Residents that have used the park, I'm sure, will find it very demoralizing to see what's left of what they considered to be a very beautiful urban park," said Jim Stomp, the park's site manager.

"The Fish Creek Valley and Fish Creek Provincial Park ... they'll be forever changed by this flooding event. And they'll never be totally restored to what it once was."

The park is now closed and officials estimate it would take months to repair.

About half the park's 110 kilometres of pathways have been eroded away, and the rest are damaged or need to be cleaned up, officials said.

Stomp said people have been coming to the park to see the destruction, but he asked them to stay away.

"We would prefer they stay out of the park until we start reopening those facilities," Stomp said.

"But if they are coming to the park, we ask them to exhibit extreme caution and to stay away from any of the water areas."

A restaurant and driving range at the park remain open and most parking lots weren't damaged.

The cost of the damage isn't yet known.