Simply move to the end of the area by swinging trapezes, jumping over the gaps, and hurrying the hell up as things collapse all around you. It's much easier than it looks (and in real life you'd be dead after a few seconds, but it matters not), so just press onward until you reach the last house, in which you will have to face a riot shield enemy. [100 XP]. Use the same tactics against this ******* like you did with the last sub-boss; dodge to the right, then unload on him. Search the room for [ARROWS x2] and a [SALVAGE BAG]. Remember you can now set fire to this bag; don't forget to immediately collect it, since it's missable. (Not like this really matters, but it's true nonetheless.)
The 'Cliffside Vista' day camp can be found up ahead, and using it unlocks [DOCUMENT - #4 LARA'S JOURNALS (UNNATURAL STORMS)]. Move through the tunnel. [100 XP]. You can find some [SALVAGE] to your left, inside the alcove. As you head upstairs, reload your weapons since another shootout is about to happen. Lara will be hoised upside down, after which you'll need to kill three enemies and shoot the pulley. You'll acquire some rope after this, allowing you to pull away any small fences around the area behind which your enemies are located. To use rope arrows, use RB or R1. You'll first have to pull a pillar from underneath the cabin; the firefight really starts after this.
This can be a tough firefight if you don't immediately dispatch the molotov cocktail-thrower inside the building (but watch the crossfire from the walkway as well). Dispatch the guys on the walkway after dealing with the pyromaniac; rope arrows can destroy the fences they're hiding behind.
: If you're really quick, you can loot some of the bodies floating down the river before they fall off the cliff.
Look for some [ARROWS] on the ground and look for an [XP BOX] on the ledge across the river. After this, pull the crate with rope around it closer (by using a rope arrow). Climb it and follow the walkway until you reach a river. You can create a rope bridge by standing next to the rope attachment spot and shooting an arrow into the rope in front of you. Upon close inspection, however, there's also some rope high above attached to the hut on the upper left. You can only create one rope bridge at a time at this spot, so choose the last option to collect the [XP BOX] on the nearby ledge.
[ARROWS x2] can be found next to the arch, plus some more [ARROWS] in the hut to the left. Destroy the door with a rope arrow and make your way to the end of the tunnel to meet up with Roth again. [400 XP].