It's a rescue mission.  You have to go out into canyon country and save people and animals from the rising flood waters.  If you're too slow, they will drown! 

When you've loaded your helicopter with people, take them to Devil's Tower where they will be 'safe and sound' from the water.

You'll be using a bungee cable to free fall towards the people or animals on the ground, so make sure you aim well and try to grab them before you spring back up towards the helicopter.