The falls are not a single straight drop but a long diagonal sandstone ledge that runs across the river at an angle, with the highest portion on the southern bank tapering down toward the northern. The geology dates from the Carboniferous period; the same sandstone bed runs through much of the Allegheny Plateau and outcrops as cliff faces and waterfalls wherever river erosion has exposed it. The Kanawha cuts across the bed here, and the harder sandstone has resisted downcutting while the river above and below has cut deeper. The result is a wide cataract: the river is hundreds of feet across at the falls, with the water spreading over the entire ledge in a long curtain rather than the concentrated plunge of a vertical waterfall.

Just upstream from Kanawha Falls, two of the most consequential rivers in Appalachia merge to form the Kanawha. The New River, which runs upward from North Carolina through the famous New River Gorge of West Virginia, joins the Gauley River, which drains the mountains east of Charleston. At Gauley Bridge, these two rivers become the Kanawha. About a mile downstream, the new Kanawha River reaches the falls. So the falls are not just a barrier - they are the place where the assembled flow of two large mountain rivers makes its first major change of character. Above the falls: mountain torrents, gorge whitewater, the Gauley's notorious Class V rapids during fall dam releases. Below the falls: a navigable lowland river that will carry barge traffic all the way to the Ohio.

The first hydroelectric plant at the falls dates from around 1899, making it one of the oldest continuously operating hydro stations in the American East. The plant has been rebuilt and modernized multiple times. In 2010, a major rehabilitation began, with the facility returning to full operation in 2012. The dam at the falls raises the upstream water slightly to feed the powerhouse intakes, but the falls remain mostly visible as natural cataract - the dam is a low structure that does not eliminate the waterfall's character. The Glen Ferris Inn, immediately above the falls on the south bank, originally housed managers and workers from the hydroelectric and aluminum operations that the falls' power made possible.

The U.S. Geological Survey has continuously measured streamflow at Kanawha Falls since 1877 - one of the longest hydrologic records in the United States. The record shows how flood discharges have changed across more than 140 years. In the twentieth century, construction of three reservoirs on the upstream rivers - Claytor and Bluestone Lakes on the New, and Summersville Lake on the Gauley - cut the estimated 100-year flood discharge at the falls roughly in half. The reservoirs trap floodwater, releasing it slowly, and dramatically reduce the peak flows that historically devastated downstream communities. The falls themselves, which once carried apocalyptic floods at irregular intervals, now carry a more managed flow. The river is calmer than it used to be, by design.

From the air, Kanawha Falls is a wide white line across a broad river, with the small communities of Glen Ferris on the south bank and Kanawha Falls (the community shares the name with the natural feature) on the north. The Gauley and New rivers meet about a mile upstream at Gauley Bridge, visible from cruising altitude as a Y of three water surfaces becoming one. The Glen Ferris Inn occupies its small flat on the south bank above the falls. The hydroelectric powerhouse sits at the falls themselves. Downstream, U.S. Route 60 follows the broader Kanawha as it begins its eighty-mile run toward Charleston and beyond to the Ohio.