How to determine locations for events on a hex board.

I sense that your game produces a lot of random events which the players are forced to either anticipate or respond to. I would challenge you to think about how these events might be generated by card play or actions by the players rather than by chance from the game mechanic itself.

A complex system can be unpredictable and deeply complicated without any chance as long as there are enough interactions between its components and those interactions have the capacity to create feedback loops and self-reinforcing phenomena. Because non-linear systems with a large number of agents are difficult for us to comprehend, they can generate events which appear to be the result of chance and spur the players to think deeply about causal mechanisms.

If it is a complex system, the players will effectively inadvertently create their own events and you may not have to address the issue of what direction lava flows or what pond floods. Each of these things may be the consequence of a lot of interlocking factors... but all completely determined by the actions the players take.

Just a thought.

In a 4-player setup, I can imagine each player sitting in a cardinal point: North, South, East, West. To do that, place a fixed compass tile somewhere handy.

Then state that the lava flow or whatever large area event will spawn to in the card description. i.e. "The Volcano erupts, and lava flows to the tiles N, NE & E."

As how to assign the tile that the event will affect, you could have the back of the event cards matching the background colors of the tiles. Forest tiles event will have green backgrounds, swamp events cards will have a black back similar to the swamp tile, etc.

If the event is onset by the player entering a certain area, you know which tile deck he has to draw his event from.

If the event is spawned randomly each turn, have the first player draw the card, and have the card depict the tile number (1st, 2nd, 3d, etc). So what you do is start in the top left part of the map the first player is facing and start to follow the lines as if you where reading the board, until you reach the "1st, 2nd, 3d, etc" tile the event depicts. i.e. now you'll have "The (2nd) Volcano erupts, and lava flows to the tiles N, NE & E."

Not sure if this is clear. Hope you get what I mean. Keep thinking!

I suggest labelling the tiles with different icons, and putting icons on the cards.
When an event card is flipped, flip another card and look at its icon. If that icon only matches one tile, the event happens on that tile. Otherwise, the player with the fewest points chooses. (If there are few enough tiles that each one has a different icon, you won't need to resort to player choice; just flip cards until you flip one with an icon matching a tile on the board.)