Wilderness Tsunami

Tsunamis, sometimes referred to as tidal waves, are crushing waves of water caused by underwater earthquakes, volcanic explosions, landslides, or even asteroid impacts.

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Tsunamis are almost undetectable until they reach shallow water, at which point the mass of water builds up into a great wave. Depending on the size of the tsunami and the slope of the shore, the wave can travel anywhere from hundreds of yards to more than a mile inland, leaving destruction in its wake.

The water then drains back, dragging all manner of debris and creatures far out to sea. The exact damage caused by a tsunami is subject to the GM’s discretion, but a typical tsunami obliterates or displaces all temporary and poorly built structures in its path, destroys about 25% of well-built buildings (and causes significant damage to those that survive), and leaves serious fortifications only lightly damaged. As much as a quarter of the population living in the area (including animals and monsters) perishes in the disaster, either swept out to sea, drowned on shore, or buried under rubble.

A creature can avoid being pulled out to sea with a DC 25 Swim check; otherwise it is pulled 6d6 x 10 feet away from shore. Waters after a tsunami are always treated as rough or stormy, barring magical conf lict. A creature caught in a collapsing building takes 6d6 points of damage (DC 15 Reflex save for half), or half that amount if the building is particularly small. There is a 50% chance that the creature is buried (as for a cave-in), or the tsunami may tear the building apart, freeing the creature from the rubble.