the ground sinks into the soil and is evaporated or runs off
slowly. The portion that is absorbed by the soil is taken up by
the roots of the trees and plants or goes to supply springs and
watercourses.

The power of the trees and forest soil to absorb water regulates
the rate at which the rainfall is fed to the streams and rivers.
Frequently it takes weeks and even months for all the waters of a
certain rain to reach these streams. This gradual supplying of
water to the streams regulates their flow. It prevents floods and
freshets. Careful observation and measurements have shown that
unforested regions will discharge rain water at least twice as
fast as will forested districts.

The stealing of soil by erosion occurs where run-off waters are
not obstructed by forest growth. Silt, sand, and every other kind
of soil are swept from their natural positions and spritted away
by the foaming waters as they surge down the steep slopes. The
stream or river which is flooded by these rushing waters roars
down its narrow channel, tearing loose and undermining the
jutting banks. In some cases, it will break from its ordinary
course to flood exposed fields and to carry away more soil. As
the speed of the stream increases its power to steal soil and
carry it off is increased. Engineers report that the carrying
power of a stream is increased 64 times when its rate of flow is
doubled. If the flow of a river is speeded up ten times, this
raging torrent will be able to carry one million times as much
foreign material as it did when it was flowing at a normal rate
of speed, causing inexpressible damage and destruction of life
and property.