The site of the new Powerhouse Museum has been inundated with floodwaters from the swollen Parramatta River, underlining the vulnerability of the $1 billion project to flood.

The ground floor of the four-level car park and the grassy riverfront was partially submerged in an area where the museum is to stand.

The inundated car park. Image taken 6.45pm Sunday evening.

Nearby, on the western side of the Lennox Bridge, the inundation was so severe site buildings for a new high-rise were seen to be teetering close to the river in video footage taken by residents.

A spokeswoman for the Powerhouse said the new building would have withstood the flood event and all exhibits would have been safe.