Stampede! Encounter table cascade

At a lake today all was quiet, then suddenly two herons took off and everything else panicked and it went from idyllic to chaos in seconds - ducks, pigeons, herons, crows - no doubt squirrels dived for cover too but they were drowned out. An encounter table should have a cascade effect - something like roll 2d4 more times and have them all happen at once - the dragon woke up, got the goblins running around, they let out the zombies, the bats are fleeing - general chaos throughout the dungeon. This does not have to be the impossible challenge of hundreds of HD worth of foes - the rolling chaos provides ample cover for a party that decides to just bug out, or potentially make a thrust onwards to glory. No need to be stealthy in this hullabaloo and whatever you run into may well consider themselves to have bigger problems just now. Typically an encounter pulls in another as reinforcements or generally as an escalation - here I suggest the alternative of running it up to high chaos and…