The Welland Canals Parkway Trail offers one of the better off-road running options outside of the immediate Niagara Falls area. This 36 km path follows the Welland Canal between Lake Ontario in St. Catharines to the Lake Erie shore in Port Colbourne. This is a popular spot for cycling, but also great for running. Generally flat, with water views much of the way, and surfaces alternating between gravel and paved. In Welland, there’s another trail alongside the canal on Merritt Island.
The closest sections to Niagara Falls are about a 15 minute drive west, off Rt. 20; further north, near Thorold (Route 57); or further south at the Port Robinson Ferry Terminal, where a bike/pedestrian ferry will whisk you across the canal to join the trail.