We just had a freak storm. 7" in just a few hours after days and days of rain, and one of the pastures turned into a wide, raging river. The current also took out our main driveway. I realize this is probably a once every 100 years type of thing, but the wire fence is a disaster. Really loaded down with debris, limbs, mud, etc.
So one more thing to think about, that I hadn't before, is if there is even the smallest chance water will go through the area. My field was normally dry area--at most the low area would get a little water after heavy rains, but there isn't a tiny creek there or anything like that...normally.
There is no perfect solution, honestly. My idea would be v mesh/flex fence top board/hotwire on inside. With your flooding a board fence could have been splintered and destroyed or trees down and boards gone. No such thing as the perfect fence.
A conclusion is the place where you got tired of thinking. (Steven Wright)
I have V mesh (no climb) but it is 5' tall and zinc coated. I highly recommend the height so they won't hang over it, and the zinc keeps it from rusting. I had the fence installed by pros that drove (pounded) the posts at 8' and that fence looks as good 6 years later as it did the day they installed it. It goes up hill and down, too. I have also not had one horse get into trouble with it. I do not have a top sight board (nothing to chew on that way) and they see it just fine with the posts being only 8' apart. It maybe more expensive than 4 board or reasonably close in cost but worth every penny.