The Earth as Modified by Human ActionMarsh, George P. (George Perkins)
History
The Earth as Modified by Human Action
Marsh, George P. (George Perkins)
Conservation of natural resources; Human geography; Nature -- Effect of human beings on; Physical geography
The Italian journals of the day state that the province of Brescia and a
part of that of Bergamo, which have heretofore been exposed to enormous
injury, after every heavy rain, from floods of the four principal
streams which traverse them, in a great degree escaped damage in the
terrible inundation of October, 1872, and their immunity is ascribed to
the forestal improvements executed by the former province, within ten or
twelve years, in the Val Camonica and in the upper basins of the other
rivers which drain that territory. Similar facts were noticed in the
extraordinary floods of September and October, 1868, in the valley of
the Upper Rhine, and Coaz makes the interesting observation that not
even dense greensward was so efficient a protection to the earth as
trees, because the water soaked through the sod and burst it up by
hydrostatic pressure. [Footnote: Die Hochwasser in 1868 im Bandnerischen
Rheingebiet, pp. 12, 68.
Observations of Forster, cited by Cezanne from the Annales Forestieres
for 1859, p. 358, are not less important than those adduced in the text.
The field of these observations was a slope of 45 degrees divided into
three sections, one luxuriantly wooded from summit to base with oak and
beech, one completely cleared through its whole extent, and one cleared
in its upper portion, but retaining a wooded belt for a quarter of the
height of the slope, which was from 1,360 to 1,800 feet above the brook
at its foot.
In the first section, comprising six-sevenths of the whole surface, the
rains had not produced a single ravine; in the second, occupying about a
tenth of the ground, were three ravines, increasing in width from the
summit to the valley beneath, where they had, all together, a
cross-section of 600 square feet; in the third section, of about the
same extent as the second, four ravines had been formed, widening from
the crest of the slope to the belt of wood, where they gradually
narrowed and finally disappeared.
For important observations to the same purpose, see Marchand, Les
Torrents des Alpes, in Revue des Eaux et Forets for September, 1871.]
Public-domain text, read in full here on John Shaqi.
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