You can see the mountain slope in the background.....the trail actually follows that silhoutte that goes off to the right and gets steeper out of the picture. Doesn't look like much, but I couldn't imagine ever riding up or down it....it is also very narrow with no room for error. But, some horse did it apparently.
Taking into consideration the footing type/trail conditions, I might gait down a gradual slope.
If he is balancing himself, and not getting rushy, and paying attention to his feet, and the overall terrain is just kind of rolling, I don't have a problem with maintaining an easy, consistent forward-moving gait rather than bringing him back to a dog-walk at the top of every hill before we descend.
To clarify - this is not something I "let" my horse do - just as I don't "let" him take off running up hills, either.
He has to be balanced, keeping his weight back and thinking about where he is and not where he wants to be, not heavy on the forehand or rushy.
If in doubt, slow down and walk it. Especially on unfamiliar trail.
There is no shame in that. . .and you and your horse will stand a better chance of living to trail ride another day.
If you have a ditch, your horse needs to be trained in hand to never rush up or down slopes. Your horse must listen to "walk on", "halt", and "back", and be very light to this in his halter and lead. A somewhat shallow ditch makes a great training tool. Always lead to the side and never in front. You demand that you horse walk down and halt after only a few steps at a time. Same going up. Repeat until he is obedient. It is possible for a horse to trip and flip on you going downhill under saddle. Maybe it won't happen, but most of us don't ride horse in any better physical shape than ourselves. This is an obedience exercise and your horse will be more fun to be around if you train him to it. =D
At this point in the year our girls have had a long time off over winter and they take it steady down hills by their own choice - seems like they know best and often have more common sense than we credit them with
Once they're fit they will go a lot faster if asked depending on the actual slope - but the 'if asked' is the thing to focus on. Our 2 drafty types cope way better with steep hills than the others.
We had a pony that could gallop down anything with total balance though the thing bsms posted would have slowed him down - he'd have probably tried to jump from top to bottom and landed in a big heap
Zig-zag down steep inclines, but always at a walk..Other wise it becomes a habit to want to trot all the time down or up hills..(I love to trot and canter up hills - and have to stop that because it does create habits if you do it all the time) My horses would see a hill and think trot/or canter automatically. So now w/my new guy it will be always at a walk unless I ask otherwise.