Looking for an estimate of hiking speed at night:
Terrain:
6 to 7 miles top.
About river crossing:
What kind of river can you wade across?
How deep? How fast? How wide?
What if you swim across?
Limited only by your stamina?
Thank you very much for your help. 
How many people are going? Are you doing this for fun? A stroll in the woods? Snipe hunting? Or do you need to cover that distance as quickly as possible? What gear are you bringing? What navigational tools are you using? There’s not enough info in the OP to answer the question.
How experianced are the people going. If you are taking Special Forces troops then they could probably cover that distance in the forest faster than some people could run it on a track. As to fording rivers it also again depends on experiance, and current. The SF guys could swim a fast moving croc infested river, and come out the otherside with a new pair of boots, and a nice purse for their wife. It all comes down to how often the people going have done this kind of stuff before, and how comfortable they are doing it.
-Otanx
Hiking speed usually falls in the 1.5 to 2 mph rate. Night hiking in areas where there are not full of hidden trip hazards and have good footing, with a headlamp, you should be able to maintain that speed, if you are not using a light I’d go with a 1mph estimate.
As for rivercrossings, it is really to broad a question to answer, just too many factors. Usually when a hiker gets to a river/stream they will look for a ford (series of rocks that can be used to hop across, or a Explorer SUV 
) or a bridge. Barring that they might go further up or down stream to find one, barring that they may make a ford by placing rocks in areas, or a bridge if a tree is ready to go. After that wading in the next option, which 2 hiking sticks help a lot as the river bottom will be slippery. Swimming would work if you are chased by a hydrophobic bear, or if the water is calm.
kanicbird has the basics. 2MPH is a good pace on fairly easy terrain in daylight, on flat you can do up to 3MPH. Add nighttime, a group (which is always slower than solo) and some inexperienced hikers, and you should count on something like 1.5 MPH over easy terrain with good headlamps. Get headlamps, they work much better than handheld flashlights. Everyone should have one, preferable two sources of light per person.
Most stream crossings can be rock hopped, but it’s much easier in daytime than at night in unfamiliar terrain. I ususally bring a pair of Tevas and will wade across anything that is up to knee hight. Deeper than that, especially in cold fast moving water, can be quite dangerous. It’s not the kind of thing I’d want to try at night with a group unfamiliar with stream crossings. A rope is real handy in those cases. People underestimate the force of moving water and can be swept downstream if not careful.
If you have to swim, you shouldn’t be crossing it at night in unfamiliar terrain.
Another major variable is whether there’s moonlight. A clear night with a full moon and you can get by easily without lights. Clouded in, no moon, and you could be at crawling speed without a light.
For a fit person, in daylight, without a pack, not up steep hills, and not in a large group, I think 2MPH is a very very relaxed pace. In fact, 4 MPH is reasonable. Adjust down as darkness, packs, terrain, etc. come into play.
Except in the kindest of climates, you don’t really want to be swimming across rivers at night. Cold and wet is no fun when you’re hiking.
Unless you are very familiar with the stream bed where you plan to cross, I would advise against trying to wade any river at night. There are shelves, holes, ledges and drop-offs on almost all river beds, not to mention slick rocks and other debris that can be dangerous. Step off a shelf into a deep hole carrying a backpack, and it could be curtains.
Unless it’s completely clouded over far from civilization, or it’s a well-maintained trail, you’d probably be better off with zero sources of light per person. With a flashlight, you’ll see well whatever is closest to you in the direction of the beam, but you’ll be hopeless at seeing anything else. If, for instance, there’s a little underbrush, the flashlight will clearly show you the top of the underbrush, but you won’t be able to see the solid surface underneath it.
And to reiterate what others have said, unless the stream is shallow enough to only come up to your shoesoles, or narrow enough to just hop over, I wouldn’t try to cross it at all at night without a bridge.
…But come to think of it, given also your question about night boating, this is probably for a historical story, where the characters might have some stong incentive for crossing rivers and such (to get back to civilization, or to raid an enemy fort, or whatever). In that case, you’d probably send one man (your strongest swimmer, or the guy most familiar with the terrain, or whatever) across with one end of a rope, and tie it securely to trees on both sides, then have everyone else cross using the rope. Depending on the river, this could be hand-over-handing over the water, or wading along the bottom holding onto the rope for security, or pulling oneself through deep water with the rope. In any event, expect your hikers to end up completely and totally miserable: Even if the temperature, clothing, and level of activity are such that the cold won’t be dangerous, it’s still not any fun to be hiking along in the dark half-soaked.
Depends on the trail. (Most of my hiking is in New England, so keep that in mind.) Above treeline or on one of the old RR bed trails in the Pemi, yes, hiking with natural light is quite good. But once you enter the woods on the narrow, rocky trails, a headlamp will definately speed up your hike. You do sacrifice side vision, and you have a bit of a tunnel effect, for many hikes its much more efficient and definately safer.
Is Chronos correct? Do you need facts for a story? Are they soldiers crossing a river at night? If so, let us know. 'Cause I’m sure there are pleanty of people who can share stories of nighttime very crossing ops.
I hope this post is theoretical.
Iter , if you are as inexperienced as the question sounds, then please don’t go hiking and crossing rivers at night. Enjoy day trips first,safely. Then you’ll know enough that you dont need to ask
Thank you for the overwhelming response.
But please don’t be worried.
You guessed right, this is only a theoretical question. But damn, nothing get pass you guys.
I got exactly what I needed. About 1 ~ 1.5 mph as a conservative estimate. River crossing should probably only be attempted at fords.
Thank you again for your help.
I’ve done plenty of hiking at night, either because of desire or necessity*, on terrain from extremely rugged trails to pan-flat logging roads. I’ve always used a Petzl headlamp, both the incandescent bulb and LED varieties. I actually kind of prefer the former, as you can get a nice focused beam with the old-style headlamp if you need it to see a greater distance (like down a steep pitch), and the broader spectrum seems to improve contrast. The LEDs are very lightweight and efficient, though.
Anyway, speed at night depends so much on how steep and rough the trail is, I find it difficult to come up with a blanket estimate for how it will alter your normal hiking rate. On easier surfaces, I can amble along just as quickly as in daylight. I’ll even go at a greater pace, sometimes…because it’s dark out and I want to get to the campsite, dammit! I once hiked late down the Great Gulf trail from the summit of Mt. Washington in NH, and everything below the treeline was traversed after sunset. That’s a difficult trail, even beyond the bare headwall, with big boulders everywhere, lots of erosion (due to the steepness and thin topsoil), places where the trail skirts ledges right above a raging stream, etc. It’s a challenge in daylight. Anxiety slowed our party down considerably (probably to about 1 mph) until the slope felt like something less than straight-down. Once the grade levelled off a bit, it we all got used to navigating with headlamp-vision, and were able to move at a good clip well before the trail became wide and reasonably flat. I’d say if you’re experienced and not prone to excessive worry about falling, hiking at night needn’t be a big deal with the proper equipment.
Water can be tough. Unless the surface is very still, and the water crystal clear, the reflected and scattered glare is going to make a light source less than useless for seeing differences in depth or other submerged obstacles. If you must cross a river at night, and it’s wadeable, use your hiking poles to both steady yourself and poke around ahead of you to carefullly test your footing. The light will only help you with stuff that’s above the water. You’ll want it if the bank is loose and steep, though, obviously. If it’s too deep to wade, and the current is greater than what you might find in your average bathtub, I simply wouldn’t do it.
*My most harrowing night experience was hiking the last third of the Dusky Track between Supper Cove and the Loch Maree Hut, in Fiordland N.P., New Zealand, in moonless dark, with my shit-scared wife. That story would fill a thread, though, so I’ll just leave it at that.
Nay, nay! I say unto your face!
Tell you what.
You start the thread about wives in the woods, and I’ll add my story about how mine (pre knot) was afraid that I stopped the car in deepest darkest part of Arkansas just to kill and bury her.