The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-09-19
TO PREVENT AVALANCHES.
METHODS ADOPTED WHERE THESE
VIsITATI0NS RI COMMON.
Various Kinds OF Avniauches and tho Causes
That Produce Them-Tho hest Preventive
IL n Growth or T~rees-Othcr nnrriers.
From the Forester.

Those best known are the so.cRllcd ground
Slides" which arc for the most part detached
in spring when warm weather opens. and cs.
pccially during the mild south winds. When,
In consequence of these causes, n mass OF
snow covering the earth to a depth OF perhaps
several metres begins to melt, the water
trickles through TO the soil, and IL the slope is
sufficiently great, 1t flows of between tho
ground and tho bed Of snow, thus looscning the
hold OF the latter, which, from It's weight Of
melted water, begins to move unless held fast
by the uneven surface of the ground.
II, on the other hand, there Is a snowfall in
winter time, during cold weather, the snow is
then fine and dry as sand; 1t Is then not sus.
ccptible of becoming packed and OF adhcring
to the ground, but rests on 1t as the lightcst Of
coverings. On a steep, bare mountain side the
least occasion, therefore, such as n puff Of wind.
n falling stone, or the chamois's tread, will
suffice to set In motion this snow mass, then
called n dust avalanche This dust ava
lanche, not improperly to be compared to n
snow cloud descending upon the valley with
tremendous speed, causes the air to DO com.
pressed and driven with cvcr.incrcasing We.
locity as II hurricane before the avalanche.
The enormous force of this air current is per.
ceptible at great distances. 1t blows over the
wooden huts and stalls like card
houses. and often lays low whole forests on the
opposite aide of the valley.
A third sort Of avalanche arc the socalled
glacier avalanches, which can be seen and
heard every warm summer day among the high
Alps, on the prccipitous slopes covered with
eternal SHOWS, as, for instance, on the northern
slope of the Jungfrau, as seen from tho Wen.
germ Alp. These avalsnchcs arise when, through
melting. the slowly moving glacier mass Is
pushed over the edge of an overhanging prcci-
pice and breaks oif, plunging into tho valley
In ice particles resembling in form and effect
the dust avalanche, Frequent AS these gla.
tivatcd lands below.
Even though the ground and dust avalanches
do not possess such Immense power, it is never
thelcss enough to destroy in the valleys even
the strongest works of protection; therefore
only exceptionally are these resorted tot i.
more customary to strike at the root Of the
evil and to prevent Its cause. A forest affords
the best protection against ground and dust
avalanches. When steep mountain sides are
clothed with wood growth even IA deep snow
covering cannot detach itself. Particularly
are mixed irregularly together, the snow is
held fast and Obliged to melt where IL falls.
plies great difficulties and demands great sac.
rihce of time and expenditure OF labor and
money.
In the first place. in rcforestlng such regions
II becomes necessary to prevent by artificial
means the snow mass from sliding down until
the forest has grown big and strong enough
to perform again this office itself.
The usual means, and one employed every
where Il the depth OF soil admits, Is the plan
OF establishing bermen and palisades. Hori-
zontal terraces so to 80 ccntimetres wide are
ranged above each, other 3 to 10 metres
apart. according to the incline OF the slope. and
rows OF stakes are driven in along the outer
edge of the solid natural soil. These stakes are
at least $50 ~centimetres long. and IL to Ii cen;
timetrcs thick. and at distances OF about go
ccntimetres are driven for half their length
into the ground and wcdged fast with stones.
II the soil is not deep enough for stakes TO find
"a firm hold. then the so.called snow bridges are
constructed. These consist of logs or beams
supported by solid wooden trcstles. and, rum
ming horizontally on the declivity, they serve
as a support to the stakes, which are driven in
at a distance of 20 to 30 centimetrcs, not, how
ever. in ii vertical direction, but about perpen-
dicular to the incline OF the mountain side. The
long beams are on an average % to 30 cent?.
same dimensions as those used in the pail.
sadcs. Together with these constructions in
the localities where avalanches take their start
reforestation must go hand in hand. so that, in
view OF the extremely slow growth in Alpine
regions. the stakes and snow bridges may
not become rotten and worm.eaten before the
young forest has grown up sufficiently.
The bermen,,, or mountain terraces. are es.
pecially suitable places for setting young plants.
but they are also set in between the palisades,
in fact, at distances OF 100 TO l40 %ccntimetres.
so that on an average about 900 plants per
hectarc are the result.
such close grouping is necessary. SO that as
soon as possible the trees may close up; they
then give each other mutual protection. and
as n consequence their growth IS FASTENED.
As regards the species planted in such places
fir ,Piced e~rcciSd,. the larch ,LdrLr European,
the mountain pine 'Pinns mont0ndI an dthe
ceubran pine IiHHS ccmOrdl are alone con
sidcrcd. OF dcciduOus trees, but few varieties
reach into the higher attitudes. Such are the
mountain ash !Sor6u$ ~aImcupdrinl and the
ties do not form n solid stand, suitable for n bar
ricr. they are Of minor importance.
While the highest peaks OF the Swiss Alps
reach anta!titude Of over 1900 metres above
the sea level. and the 10 Ncr limits OF eternal
snow vary from 40" to 500 metres. The
mountain pine and larCh Mt 1000 to loo
metres, and the cembrnn pine at 200 TO 2,ioO
metres above the sea.
Above the timber line the building of ava,
,anche barriers is mostly q hazardous and dn,
s osoqs y"G accessibfo rocky u" prc %Gi Sc."" but t only 1niy
to those steep. smooth declivitf,s which often
begin on the ,topnost ridges far above the
timber line and give rise 10 avalanChcs which
plunge far down 10 the inhabited and cultivat,
cd valleys below. In such regions the use OF
not %SoG only because az il Would have to be carried
on the back long Distances T y HILL but because
Of fioi Its 8, li MnrE q, du6bS S mni NJ. iNea gor 1t Is a y g yaGG
stone material alone fultils the requirements
HORIZONTAL walls Of dry masonry are built,
Gle, but nj the same time one OF great resis
lance TO the snow masses. The height Of the
at least one metre. The Foundation is made
so strong that with nm inclination OF o%nc.hftf
metre of the outer side Of the wall there is still
At the top u width of about sixty ccntimetrcs
The line OF foundation should incline slightly
downward from the outer to the inner edge
II is not ncccs airy, to dig down to a rocky bot
tom. yet the wall must never be placed OF
made ground. but only on natural soil. As il
the case with the rows OF wooden stakes tn
walls. too, are built at different distances on
aD0ve another according TO the inclination d
the slope; The most eligible places arc whcr
II slight tattening OF the slope would NATURAL,
favor the gathering OF n mass Of snow hclint
the wall. II necessary the space is ARTIFICIAL!
extended. For the length OF the walls nc deli
mite rule can be given. II depends upon loca
conditions. Rather are two short walls TO h
preferred to one long one, Ms the two short ones
broken by II short space between, accomplish
the same object as II single wall as long n
both. plus the interval.
In the long walls, or in those where gutter
might be formed, il Is desirable to construct on
or more water outlets IN the foundation, tina
, IL. where the substratum is earth, as other
wise. In the spring thaws, the melting waite
behind the walls generates into the soil an
may occasion landslidcs.
The greatest danger In this sort Of cor
structi0n above the timber line consists in III
formation OF so.callcd upper avalanche
Surprising the stocp slope to be covered with
snowfall so deep that the walls and the NJ
evcnncss OF surface occasiOncd by them entire
lysdisnppcarS, and then in succession warm IN
cold weather follow each oil or. there ihay i
Q formed on tho surface Of the snow II stroni
hard, Icy crust. should more fresh snow IA
n -. a 49,, ,u, tlut a N,tIl - nrt In Ali