If there was ever any doubt as to the effectiveness of security fencing, an incident in the US has disproved that this week.

Security fencing successfully prevented a 50 tonne boulder from crashing onto an access road when a rockslide started at Niagara Falls yesterday (Wednesday March 9th).

The road, which leads to the New York Power Authority's fishing pier facility at the base of the Robert Moses dam, was closed to pedestrian and vehicular access after the incident, the Niagara Gazette said.

Spokesperson Lou Paonessa said one large rock and several smaller ones slid down an embankment and into the protective security fencing, stopping it from reaching the road that is used by pedestrians to get to the pier.

"It did what it was designed to do," he told the newspaper.

The Niagara Falls waterfalls straddle the border between Ontario, Canada, and the US. It is thought that 6 million cubic feet of water fall over the water line every minute.ADNFCR-3337-ID-800455338-ADNFCR