my main survival concern is much like yours..the red PFD under my name carry's the gear i would need if i lost my boat and packs.so my question is what is the worse that you are expecting? lose everything and swim to shore,lots of rapids?-water temps?solo?..is this a well know and used river? semi wilderness or play boats?
i carry everything to takes to "camp"--start thinking there..fire-food-shelter..you may to do a search under my name for a layout and breakdown of my kit,the photos were post a couple years ago...
don't skimp and go cheap on this as it could save you life and a 99 cent foil "blanket" from the drug store is not what you would want to depend on..