I have caught over 18,000 beaver and otter in the last 22 years. Most of those were catches made using a trap with a body grip trigger. In getting this experience understanding how the animals respond to water flow and trap placement was critical. When I did my “Trappin Tales” video we filmed in flooding conditions and heavy rain.
I learned that in periods of high water animals have no problem going down stream but when forced to swim back upstream will tend to climb a dam to the left or right of the most forceful part of the stream flow or be washed back. Especially the smaller ones.
In demos using a swing bar beaver trap, a trigger is shown as being able to be set with force needed to combat the water pressure. It is implied as being a great asset for stability.
Now let’s assume there is 15 lbs of water pressure the spread fingers of the swing bar trigger is holding back. That means it will take 16 lbs to set it off moving down stream or just one more pound of pressure. What about the other way? Going up stream a 30 lb beaver would have to push almost his whole body weight to make it through the trap and fight it almost all the way through to fire the trap. He is not going to do that. He is going around. He may even grab the trigger (if the trap is upside down) and not be in the trap far enough allowing a miss. Now set the trap to the side and divert to the trap with debris guiding the beaver to a set that he can walk through. Use a trap with a body grip “hanging” trigger and bend the trigger wires up just above the fast flowing water. Use a tall trap, over 14 inches. Now you are not missing anything going up or down stream. Re position trap as needed as flow subsides. You would do that with a 330 , foot hold, snare, or cage trap.