The USGS gauge on the Oswegatchie in Harrisville provides an "approximation". The benchmarks below have many variables, so make sure you assess each drop yours
At low water this rapid is a bunch on low angle slides, with multiple routes. At high water, it becomes a small slide into a hole, similar to the upper part of Sinclair Falls (Twin Falls section). Scouting can be down river left as well as a path to portage.