Man and Nature; Or, Physical Geography as Modified by Human ActionMarsh, George P. (George Perkins)
Science
Man and Nature; Or, Physical Geography as Modified by Human Action
Marsh, George P. (George Perkins)
Conservation of natural resources; Human geography; Nature -- Effect of human beings on; Physical geography
Many similar enterprises have been conceived and executed in modern
times, both for the purpose of reclaiming land covered by water and for
sanitary reasons.[322] They are sometimes attended with wholly
unexpected evils, as, for example, in the case of Barton Pond, in
Vermont, and in that of the Lake Storsjoe, in Sweden, already mentioned
on a former page. Another still less obvious consequence of the
withdrawal of the waters has occasionally been observed in these
operations. The hydrostatic force with which the water, in virtue of its
specific gravity, presses against the banks that confine it, has a
tendency to sustain them whenever their composition and texture are not
such as to expose them to softening and dissolution by the infiltration
of the water. If then, the slope of the banks is considerable, or if the
earth of which they are composed rests on a smooth and slippery stratum
inclining toward the bed of the lake, they are liable to fall or slide
forward when the mechanical support of the water is removed, and this
sometimes happens on a considerable scale. A few years ago, the surface
of the Lake of Lungern, in the Canton of Unterwalden, in Switzerland,
was lowered by driving a tunnel about a quarter of a mile long through
the narrow ridge, called the Kaiserstuhl, which forms a barrier at the
north end of the basin. When the water was drawn off, the banks, which
are steep, cracked and burst, several acres of ground slid down as low
as the water receded, and even the whole village of Lungern was thought
to be in no small danger.
Other inconveniences of a very serious character have often resulted
from the natural wearing down, or, much more frequently, the imprudent
destruction, of the barriers which confine mountain lakes. In their
natural condition, such basins serve both to receive and retain the
rocks and other detritus brought down by the torrents which empty into
them, and to check the impetus of the rushing waters by bringing them to
a temporary pause; but if the outlets are lowered so as to drain the
reservoirs, the torrents continue their rapid flow through the ancient
bed of the basins, and carry down with them the sand and gravel with
which they are charged, instead of depositing their burden as before in
the still waters of the lakes.
_Mountain Lakes._
Public-domain text, read in full here on John Shaqi.
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