As ES says, not impossible but in fact quite normal.Herein lies one of the problems with the story where a plothole may be unresolvable. The water is still flowing underneath, but the frost froze the water above, which would normally be impossible, except for the idea that this was magic.
But again, this dam may have been the "family dam" for generations.
So the text doesn't directly say that Mr Beaver had built it, but it strongly implies it, and his response is strange if it was just an ancestral dam - you would expect him to say something like, "Ah, yes, my great-grandfather built this."LWW said:Just below them a dam had been built across this river, and when they saw it everyone suddenly remembered that beavers are always making dams and felt quite sure that Mr Beaver had made this one. They also noticed that he now had a sort of modest expression on his face - the sort of look people have when you are visiting a garden they've made or reading a story they've written. So it was only common politeness when Susan said, "What a lovely dam!" And Mr Beaver didn't say "Hush" this time but "Merely a trifle! Merely a trifle! And it isn't really finished!"
how long is Narnia winters with how the witch's spell
Yes, I've wondered that too. Trade is possible, but then it seems unlikely that Tumnus would be unaware of the humans living in neighbouring countries, nor that the Witch would want contact with them. Maybe the people found ways to grow enough vegetables to live on. Someone else has suggested that maybe the Witch provided food, and her control of food was one of the ways she was able to attain and retain her power.I reread the book through with this dilemma in mind, and one thing cropped up that caught my attention:
At the beavers the children eat a tea, which includes potatoes and Mr. Beaver's beer. Also, Mr. Tumnus serves Lucy a cake. Perhaps potatoes could grow in those wintry conditions, I don't know, but surely not cereal crops. Where then did the food come from - could it have lasted 100 years?
There are explanations of course, the food was traded from other lands (though would the Witch be so thoughtful as to provide food for the Narnians) or perhaps smuggled in.
I don't know - what do you think or is it simply a plot hole?
Interesting question, although not really one that is pertinent to this thread.That's also a good point. How does a flat world have seasons?