. Bulletin of the Geological Society of America. Geology; Geology -- United States. Figure 11.—Cross-section of a river Valley having no Flood-plain. Each half of the valley has only two elements, the weather curve a b and the water curve b c. Anomalous Valleys of the great Plains.—But certain peculiar conditions sometimes intervene to prevent the development of a Hood plain where it normally belongs. Then we have the anomaly of a valley some miles in breadth without a flood-plain, which is so diametrically opposed to our ordinary conceptions of rivers that we are at once impelled to seek its
. Bulletin of the Geological Society of America. Geology; Geology -- United States. Figure 11.—Cross-section of a river Valley having no Flood-plain. Each half of the valley has only two elements, the weather curve a b and the water curve b c. Anomalous Valleys of the great Plains.—But certain peculiar conditions sometimes intervene to prevent the development of a Hood plain where it normally belongs. Then we have the anomaly of a valley some miles in breadth without a flood-plain, which is so diametrically opposed to our ordinary conceptions of rivers that we are at once impelled to seek its explanation. It is upon the great plains at the eastern base of the Rocky mountains that we find the most striking examples of wide valleys without flood-plains. The lower part of the water curve (m n, figure 12). Figure 12. — Cross-section of a broad Valley of the Plains having no Flood-plain, a l> = weather curve; b m n = water curve, of which the lower portion, m ??, is greatly extended. may be a mile or two in breadth. At the point m the valley wall begins to be well defined. The valley floor m m is also well defined, but quite remarkable for its wide departure from horizontality. The point m may be fifty feet above n. It is unmistakably a valley floor, but its steepness is astonishing and perplexing. Moreover, the anomaly does not stop with the unusual form of the cross-section. The quality of the land contra- dicts all expectations which would naturally be entertained respecting river bottoms. Instead of a uniform stretch of rich alluvium we find irregular alternations of loam, sand, gravel, gumbo and alkali patches. The best element, the loam, may indeed predominate, and hence the valley may support a prosperous agriculture; but the valley lands of the plains are generally inferior to the table lands, thus reversing the condi- tions which usually prevail. The plains are built up of incoherent masses of sand, gravel, (day. Please note that these images are extrac
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