[quote=@Lauder]
It seems a lot of our options are going to require a hefty amount of man power
[/quote]

I can think of several that wouldn't, but my lips are sealed. A couple good options have been noted. But digging a ditch to divert the flow is a good idea. Your high-manpower plans have a chance of working, too.

I'll note that there are actually a few spellcasters in your Council, and there are God-Talkers to appeal to as well.