How would using Thunderwave to stop falling damage work?

Question

Thunderwave, on a failed save, pushes a target 10 feet when it hits them in addition to doing damage. In the event that a party as a whole were falling, a creative Cleric could Ready his spell to be cast when they're about to hit the ground, by Thunderwaving the other member's of the party, directly, 10 feet in the opposite direction.

Since physics aren't really a thing in D&D, would this theoretically counter the fall damage by negating all forward momentum and setting it back to zero? I understand they'll likely still take at least 10 feet of fall damage, but that's not what I'm mainly curious about.

Answer 1

This method nets you more damage

Falling damage is dealt at the end of a fall.

PHB 183, Falling

At the end of a fall, a creature takes 1d6 bludgeoning damage for every 10 feet it fell, to a maximum of 20d6. The creature lands prone, unless it avoids taking damage from the fall.

So in order for Thunderwave to stop you from taking this damage, it has to end the fall first and then begin a new one, wherein you fall at a height of 15 ft or less. Furthermore, it must end the fall without dealing damage to you.

If you are falling and then are subjected to Thunderwave such that your fall stops and is reversed (ie, you are tossed upwards), you should take falling damage then. And now you begin a new fall from your new height.

For example: you fell from a height of 100 ft. After falling 90 ft, your Cleric (who is on the ground, right at the spot you are going to land on) casts Thunderwave, sending you back 15 ft upwards. Then, your fall must have ended at the moment you were 10 ft away from the ground when you were hit by Thunderwave.

You take 9d6 + 2d8 damage for this. Then you begin a new fall from a height of 25 ft (the 10 ft you were at, plus the 15 ft from TW), dealing you another 2d6 damage when you land.

All in all, this nets you extra damage equal to 1d6 bludgeoning, for the extra 15 ft fall, and 2d8 thunder, from the Thunderwave.

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Response to Objections:

1. Thunderwave causes forced movement, and forced movement doesn't trigger damage effects. Is there a rule that Thunderwave must trigger the damage?

   • A spell does only what it states it does. Thunderwave does not say it prevents falling damage. Moreover, the saying goes "It's not the fall that hurts you; it’s the sudden stop" which I feel is applicable here. The rules for taking falling damage state that you take damage "at the end of the fall." If Thunderwave causes your fall to end, then you must take damage.

   • There is no rule that says forced movement never triggers damage.

2. Is there a rule that the falling counter isn't reset once pushed back up? Take Feather Fall -- you don't take fall damage by just waiting to cast it.

   • There are no rules about "resetting the counter of fall damage"; however, Feather Fall specifically negates fall damage.

3. So going by (2), then if you cast Fly on yourself while mid fall, do you take damage because your fall ended?

   • PHB 191, Flying Movement seems to suggest that if you are held aloft by magic, you are not considered falling. A non-falling creature does not take Fall damage. See this answer which discusses this specific objection in more depth.

4. "At the end of the a fall... the creature lands prone..." Thus the fall ends when the creature lands. That is not to say that the creature didn't fall 100', but that the thunderwave doesn't itself precipitate falling damage

   • These are two separate sentences with independent thoughts. More accurately, it's "At the end of the fall, you take damage equal to X" and "If you take damage after falling, you land prone." If Thunderwave causes the fall to end, damage is still taken. But landing becomes inapplicable as you do not land when hit by TW in this way.

Answer 2

This is mostly likely a DM Discretion issue, but what follows is some guidance:

In order for Thunderwave to successfully push you 10' away from the ground, the Cleric would need to have done the following:

1. Depending on initiative order at the time of falling, there may not have been an opportunity to ready the action. For the sake of this discussion - there was sufficient time.

2. Cleric would need to fall first and be 'below' the party. This would allow him to "push" his party 10' up prior to hitting the ground.

3. The party would need to be directly above and in range of the Cleric. Your mileage may vary on how you interpret in range.

4. All party members would still have to make the save against it and take the 3d8 Thunder Damage (either full or half depending on save state.)Further discussion on saving throws can be found here.

If those conditions are met, then the question arises as to what happens.

The cleric would of course hit the ground with regular falling damage.

The party, after falling X feet, would now be pushed back up, only to fall back down final 10 feet to the ground.

From a pure calculation point, you have the original X distance, then they are pushed back up 10', only to fall again. The original fall is still occurring, but you have moved sent them back up 10' in order to fall.

It is unknown if falling damage is based purely on distance, or on an assumption of speed/momentum. However, given that the falling damage is calculated purely on distance, you have still falling the full distance, plus an additional 10' AND the thunder damage.

However - I think there is a case for saying the push 'resets' the falling meter and it's only 10 feet that they have fallen (if you timed it right after you hit the ground, but before your party does.)

This basically turns a Readied Thunderwave into a bit of a Featherfall. For a level One spell slot, I think this is reasonable as long as the first four conditions I listed are met.

Answer 3

The combo is outside the rules, and by strict RAW provides no benefit. However, many DM's might still desire to encourage roleplaying and creative thinking, and PHB p.193 states:

When you describe an action not detailed elsewhere in the rules, the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure.

In this case, I might still allow the spell to provide a sonic cushion, reducing the fall damage for the party by 10' (possibly more if the caster rolled high on Arcana). Similarly, if a player asked - I might grant the same minor benefit for say, using a fireball when falling into ice (to melt the ice) or water (to create bubbles or even an updraft). It's generally more fun to say "Yes, and" to players (but with minor benefits that don't unbalance the system).

At the very least, it can provide a narrative reason why a high HP PC survived a terminal velocity fall.