Re: [HOE] [HoE] Landslide Question

[Theo McGuckin <tsm@jlab.org>]

> Let's say you have a posse moving slowly up a steep incline covered in
> loose rock.  Suddenly (for reasons beyond the posse's control), a
> landslide starts from above them, consisting of said loose rock as well
> as a number of medium to large sized boulders.  The posse desires to try
> to dodge and/or outrun the landslide.  How would you calculate the
> pace/acceleration of the tumbling rocks?  How would you take their mass
> and acceleration into account in determining damage when they begin to
> pummel the posse members?  Would you also include some variation of
> "falling" damage as some unfortunate posse members gets swept up in the
> landslide and carried along with it? Has this perhaps been covered in
> Weird West already (or somewhere in Wasted West and I'm just not aware
> of it)?

Pulled this off a newsgroup-type post:

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To answer your question, first it must be determined what an "average"
avalanche is! Maybe this is why the newest edition of
 the Avalanche Handbook does not really give a straight answer.

 The last edition (1978) states that speeds are typically in the range of
25-75 meters per second (which is 56-168 mph) and
 that maximum speeds reach 125 m/s (or 280 mph!). These figures are
probably based on measurements of some kind.

 From my MS Thesis:  "Avalanche velocities have been measured using
photogrammetry, mechanical switches, and hand timing. Maximum measured
 speeds are 50-55 m/s. [Colbeck, Samuel C., ed; "Dynamics of Snow and Ice
Masses"; Academic Press (1980); Ch 7 Table4].
 Calculations based on indirect evidence and on theoretical models
indicate that speeds in excess of 100 m/s may be obtained in
 large paths. Mass elements within a moving snow mass may be moving much
faster than the overall avalanche velocity. Since
 the flow is turbulent, velocities within should be statistically
distributed and high speed transients should exist. Transient
 velocities up to 150 m/s have been recorded using pressure sensors.
[Shimuzu, et. al.; Low Temp. Sci., Ser A, Vol. 35; (1977).]"

 You can see that there are varying figures between sources written at
about the same time. This is because this is a difficult
 parameter to measure over any appreciable sample size of avalanches.
Studies of avalanche velocity continue to be made, but
 most are looking at velocity distributions and study one or a few paths
repeatedly.

 Now that I've gotten into this and given more of an answer than you
probably wanted, I better finish with a bottom line
 comment. Most fatalities, and many incidents involving damage of some
kind, are not the largest and fastest moving ones.
 Small ones can kill people and cause damage - keep that in mind!
--------------------------------------------------------------------

So I'd say outrunning a rock-slide is basically out of the question. You
could make some generic rules:

The rockslide starts with a certain size. If it starts as loosening of
dirt then it starts at size 1 and grows by one size every round. If it
starts with boulder breaking free then figure out the size of the
landslide from the average boulder and grows. There should also be a
maximum slide size based on the biggest rocks available.

Every round the char. must make a nimbleness check with TN equal to 5 +
the size of the rockslide as his first action. If he fails he takes 1d6+3
(falling damage?) per size of the rock slide. This damage is applied to
the legs for rockslides of size 2-4, and is massive damage for
larger rockslides. If he succeeds he takes half that damage. Rockslides of
size 1 cause wind damage as do most snow avalanches.

Escaping is simply a matter of getting out of the way. The PC takes damage
every round (+ wind, + stun check) until he can move out of the slide or
into cover.

How's that for starters?

 Theo McGuckin
	"Powerful like a Gorilla, yet soft and yielding like a Nerfball"