-- Last Updated: Feb-21-13 2:16 PM EST --
Tying a rope to a thwart, then tying the rope to a string of packs which float free if the canoe capsizes can easily result in "boat entrapment".
If one of the packs gets caught on a boulder or strainer, the canoe may continue downstream until it reaches the end of the rope end attached to the thwart. Then, if the water flow is strong; the thwart used as an attachment point may snap from the combined weight of gear, canoe, and water in the canoe. Wood gunwales may also be damaged, as thwarts are attached to the gunwales.Seen it happen.
I personally like for my packs to remain secured inside the canoe, and ideally kept below the height of the gunwales. I will tie very small items(sponge, canteen, pump, etc.) to the thwart in front of me, on a short line that presents little to no entanglement issue.