Franconia Brook Trail is a 16 mile out and back trail located near Lincoln, NH that features a river. The trail is rated as moderate and primarily used for hiking.
Great hike! Eight miles from the Lincoln Woods parking lot to Thirteen Falls campsite, where I spent the night. No one there, which provided some awesome solitude under a full moon. Six stream crossings (as opposed to the three shown on the map), all of which required some pretty plucky rock-hopping with poles to avoid wet feet.
This is a really nice trial and overall not difficult, but the water crossings were a little nutty! There were about three times as many water crossings as were on the map. And nearly all of them required taking off my boots to cross. The permanent water crossings appeared to have well positioned rocks for crossing, but they were completely submerged by roaring currents. Even my lovely water proof, gore-tex boots do nothing for a river spilling over the top of them. It was fun though, and kept us from getting too hot and weary on the first of our three day loop. On several the current warranted using poles or sticks to balance. The falls at the top of the trail by the 13 falls campsite are beautiful lots of fun to goof off in. There's actually another fork to the river behind that you can see from the shore with another very secluded waterfall.
The falls is a bit over three miles from the visitors center, about 6 miles total.
The trail is wide with railroad ties in some areas of the trail which can be annoying to walk on and with slight elevation near the falls and some exposed roots to navigate it is easy to hike. There is not much for views along this trail and the falls are small. It is a good trail to take your dog on or if you just want to get some exercise and for bicycling. Dogs are allowed (with a leash).