I know I posted about this yesterday, but this article has more details.
From the National Post:
New York officials are considering temporarily turning some of Niagara Falls into a trickle.
Plans to replace two 115-year-old pedestrian bridges could involve shutting down the water flowing over one section of the falls by building a temporary structure to redirect it to another.
It was done once before, for a 1969 study of erosion.
The result then, as now, would be a rare look at the rock formations that lie beneath the American Falls and Bridal Veil Falls on the United States side of the tourist draw, and perhaps an even more robust Canadian Horseshoe Falls, where 85 per cent of the water flows over normally.