Gunpowder Creek is located in Boone County and flows out of Florence, KY (and the Northern Kentucky/Greater Cincinnati Airport) west through a Boy Scout camp (Camp Ernst), and on to the Ohio River. Like many of the Greater Cincinnati area creeks, this one's difficulty changes with the flow. Below 1500 cfs, this creek is a nice little Class II run with some easy surf and play spots. Above 1500 cfs, the speed of the water is quite fast and some 5-6 foot standing waves form in several of the rapids. Some of the waves are quite wide as well. The difficulty doesn't get much above Class II+ (maybe Class III- with some of the bigger waves at high water), but several blind turns into strainers make for some Class IV consequences.
Overall, it averages about 40-50 feet wide, and the banks are tree-lined with lots of big sycamore trees. It is very pretty, and very little sign of civilization can be seen anywhere along the run. Camp Ernst on river right will probably be the only buildings you see.
The best rapid of the run is at the nature preserve (Powerline) and can be identified by a powerline clearing on either side of the river. Busy water and some surfing spots are scattered throughout. This area is a wood collector, so keep your head on a swivel and take your time to avoid the many dangerous strainers that can accumulate in this area. The nature preserve is also an alternate take-out if you want to skip the 4+ miles of mostly flat, moving water after this (take-out river right). Be warned if you take out at the nature preserve - the hike out is up a substantial hill (you climb 200+ feet in less than a half mile...most of it at the end of the hike).
There are some things to consider before running this creek. 1) Out of all the Great Cincinnati area creeks, this one comes up the quickest. If you are looking to run Gunpowder, you want to be on the river when the rain stops. 2) It flashes very fast and drops very fast. Understand that the flow routinely jumps 500+ cfs per hour during a moderate rain. A 300 cfs trip and very quickly turn into a 2000 cfs trip. 3) There have previously been concerns about pollution in the creek. These concerns cannot totally be disregarded, but information from KY officials suggest it's not worse or better than any of the other local creeks. Having a hearty immune system doesn't hurt either. Wildlife is abundant in the area (Great Blue Herrons, King Fishers, hawks, deer, and fish), so the water quality has improved over the past 10-20 years.
Possible alternate put-ins are upstream: 1) at the end of Running Fox Road (between the two houses in the cul-de-sac) is actually County owned propery, 2) Woodcreek Drive bridge (actually on South Fork of Gunpowder Creek), and 3) South Fork Park (also located on the SF of Gunpowder Creek; be mindful of a possible low-head dam here). Upstream might be a better option as the access points are public land and will probably add some fast-moving, fun water. As stated above, not much in the way of whitewater is present after the nature preserve.