This frequently follows land greed, and results from cutting of all trees and shrubs along the streams' banks and cultivation to the very water's edge. The consequence in this case and in many others is that all alluvial land is destroyed FIG. 2.-A strip from this field has had free transportation down the Tennessee River. Carroll County, Tenn. EROSION OF FARM LAND The yearly burden of the Tennessee River is 11,000,000 tons of soil, in large part from lands such as these. The Army engineers' report on the Tennessee River notes the extensive deposits of silt in the reservoir at Muscle Shoals already materially reducing its pondage FIG. 2.-Brush dams are an expedient for checking the deepening of gullies. If rough hillside lands were kept in wood, gullies would not form; the land would not be destroyed. Such raw spots should be planted to trees FIG. 2.-Erosion in dry gulch tributary to Fountain Creek, near Pueblo, Colo. Erosion of this kind is not an infrequent sequence of heavy rains in this region of unconsolidated soils which lack the protective cover of vegetation. Many similar arroyos can be found on the Pecos River, Río Grande, and tributaries of the Colorado River in New Mexico Valley there are a few streams subject to nearly the same influences, such as the Pearl River of Mississippi, which may appropriately be included. Fifty-seven of the Appalachian streams have 9,241.5 miles of navigable water. Most of them are navigable many miles above the tidal limit. The power which can be developed from these rivers is in many instances as important as their use for navigation, especially in those regions which are remote from coal mines. The most typical streams rise at high elevations, 3,000 to 5,000 feet, in the Appalachian Mountains where they are fed by many swift tributaries. Leaving the mountains, they flow less rapidly through the hill country of the Piedmont Plateau or the rolling farm region of the Mississippi Valley. There is an entire absence of lakes and natural reservoirs. The forest at present covers about one-third of the area of the different watersheds. Except in the most rugged mountains, the soil mantle over the greater portion of this region is prevailing deep-in many sections from 20 to 50 feet. The soils may be separated into three classes: (1) Loams and sands which are fairly permeable and have high storage capacity; (2) silts which are less permeable and have a lower storage capacity, and which, on account of their friability, are subject when exposed to most destructive erosion (pl. 14, fig. 1); (3) compact clays deficient in granulation which have an extremely low absorptive power and a low storage capacity and which erode badly but seldomly destructively. The lighter soils are the most extensive in mountains and are the sources of the steadiest perennial springs. The heavy clays are extensively distributed and cover thousands of square miles on the Piedmont Plateau. The unfavorable effect of the prevailing close-textured soils upon stream flow is further increased by the conditions governing precipitation. The snowfall is light, except in the high mountains, and the annual precipitation of 45 to 60 and even 80 inches in some localities frequently falls in concentrated showers. At several places as much as 9 inches is recorded as falling in 24 hours and at one place 22 inches within two days. Such torrential rains are destructive to steep slopes which are not protected either by a well-matted sod or by forest. Below the mountains the humus, both in forest and in farming soil. is generally deficient, the deficiency being greatest farthest south. This lack of humus is partly due to the climate and soil, which favor the rapid oxidation of humus and partly to fires and grazing, which cause its depletion in the forest. The climate is mild, the winters are short and frequently open, and the ground is not covered by snow. The summers are long, the humidity is often high, and the rainfall is irregular and concentrated. These conditions retard the formation of humus and favor its rapid destruction. The proportion of cleared land on the watersheds is apparently not excessive, but the condition and situation of much of it tend to jeopard not only the value of the rivers but the permanency of the soil as well. Unfavorable soil conditions have become far more general since 1880. The cultivation of extensive areas of hill country below the mountains, especially of the red clays in the extreme |