The three bag system.

Since I wasn't able to do any research today (thanks to two several-hours-long events about which nobody felt like telling me), I'm going to move away from weapons for a bit and talk about carrying and distributing equipment.  I call this the "three bag" system, for reasons that'll become obvious.

  First, make a bag of the smallest and most important equipment in your kit.  This is called the carry bag.  You should be able to fit some dried food, water purification tablets, a little medical kit, and other light, vital equipment in the bag, and it should be secure without you holding on to it.  You should carry everything in plastic bags or some other waterproof container.  Slipping my own preference in here, I recommend a fanny pack because it won't carry so much that you're tempted to put in too much, but has more than enough space for the things you'll need the most.  If you want to, you can also keep items in your pants pockets, but make sure that none of them will fall out when you move quickly or upside down and that they'll survive a plunge underwater.  Again, plastic bags come to the rescue.
  Second, make a bag of less important but still very useful equipment.  This is your drop bag, full of the items that'll keep you healthy if you lose most of your supplies, but "droppable" so long as you have your carry bag.  Backpacks work beautifully for this, because they won't fall off if you run but you can still get them off in a hurry if you need to dump weight.  And remember not to carry everything in here: if you need to run, you should be able to quickly strip off anything stopping you from sprinting, including this, without risking your life in the near future.
  Third, fill a bag with the heaviest, least important equipment you have.  If things get hairy, you should be able to ditch this and run while keeping all of your more important things in your drop and carry bags.  If you can retrieve the bag, great. If something stops you, though, you should be able to live off of the things in your other two bags until you find more gear.  I recommend a duffel bag because it's big enough to carry more than what you need, durable enough to survive a fall, and designed to be easy to carry.