Going Upriver

Once the party has defeated the cultists and rescued the prisoners, they continue their journey up the river (with Everett) to meet the "all-knowing" wizard who can help them unlock the artifact and guide them on their way.
It feels like there is a good opportunity here to use some skill checks in play. I suppose the party can choose how they wish to continue upstream, but they should have the choice of boating or riding at least. Either one offers opportunities to have them battle nature for a change instead of monsters.
If they travel by boat, they should be able to make pretty good time, but they will certainly meet impassable sections of river, whether waterfall or rapids. Rapids, they could try to make their way up through, with skill checks based on proficiency with water vehicles, athletics, and strength. Portaging can put them in many of the same difficulties they would face traveling by land - namely, steep trails, slippery slopes (loose rocks or wet ground), narrow trails and ledges.
This is an area of play that I have difficulty with. I have tried adding elements like this into a couple of adventures, but as much sense as they make to me while creating them, I get stuck trying to use them in play. The trouble is that ultimately there is just a dice roll to resolve the conflict. "You slip on the loose gravel, make an Athletics check or slide down the hill into the river - you succeeded. Now you're moving again." It is anti-climatic. The trick seems to be in telling the story of the passage in a compelling way, pausing to roll in order to add color to the story, without relying on the roll to tell the story.
This is a part of play that has been particularly challenging for me and my group. We have fallen into the trap of playing encounters sporadically through the year whenever we can get together. As such, we pull out a map, pick some monsters, and make up some reason to fight them. In this case, we're trying to tell a particular story along a specific quest line. I see value in creating points of conflict, and giving the players the opportunity to choose how to overcome them, rolling appropriate skill checks.
It is a difficult aspect of gameplay to write up, since it relies heavily on the spontaneity of the choices made, but some things can be outlined. I've had areas that needed to be climbed. Give them a DC to overcome, then list possible adjustments that can influence the DC. "It's a steep cliff, DC18. Fail and slide down 30 feet, but if you use a rope, DC15. Use stakes to anchor the rope and you only slide 10 feet." That sort of thing.